Prolactin responses to stress induced by a competitive swimming effort

Biology o Spo , Vol. 24 No4, 2007 . PROLACTIN RESPONSES TO STRESS INDUCED BY A COMPETITIVE SWIMMING EFFORT L. Ca asco Páez1, G.T. Luque1, C.V. Gu ié ez2, C.M. Ol as2 1Dep . o Heal h and Spo Sciences, Ca holic Uni e si y o Mu cia, Spain; 2Dep . o Nu sing, Uni e si y o G anada, Spain Abs ac . Pu pose: The aim o he p esen s udy was o in es iga e he changes in p olac in (PRL) plasma concen a ions induced by compe i i e swimming p ac ice. Me hods: Twen y- h ee males, 13 ained swimme s (expe imen al g oup) and 10 seden a y and heal hy s uden s (age-ma ched con ol g oup) ook pa in his in es iga ion. The swimme s we e assessed a h ee poin s: basal condi ions, p e- and pos -swimming compe i ion (100 m ees yle), whe eas subjec s om he con ol g oup only unde ook he basal ial. The a iables analysed we e: se e al body composi ion measu es, anxie y le el (STAI ques ionnai e), PRL and lac ic acid concen a ions. Resul s: No s a is ical di e ences we e obse ed in PRL basal le els be ween g oups. An e iden PRL esponse o p e-compe i ion psychological s ess was obse ed in he expe imen al g oup, since he PRL plasma concen a ion ose om 4.02±0.53 ng/ml (basal condi ions) o 5.52±0.53 ng/ml (p≤0.05). The PRL esponse o he compe i i e e o p oduced an impo an inc ease in i s plasma concen a ion (10.07±1.59 ng/ml), showed s a is ical di e ences om p e-compe i ion (p≤0.01) and om basal condi ions (p≤0.001). A signi ican ise in plasma lac a e le els jus a he end o he e o was ound, al hough i did no co ela e wi h PRL le els in he same si ua ion. Conclusion: While we obse ed a ema kable esponse o PRL o psychological and physiological s ess induced by a sho e m compe i i e e o in swimming, no changes in PRL basal le els we e exhibi ed wi h swim aining. Mo e esea ch is needed o cla i y hese indings. (Biol.Spo 24:311-323, 2007) Key Wo ds: Anxie y - Ho monal elease - Anae obic exe cise - Compe i ion In oduc ion The esponses and adap a ions o se e al ho mones denomina ed “s ess ho mones” which a e sec e ed om an e io pi ui a y gland, can gi e an in eg a ed Rep in eques o: D . Luis Ca asco Páez.Mu illo 13, 1ºB.03600 Elda, Alican e, Spain Tel: 00 34 968278824, Fax: 00 34 968278658; E-mail: [email p o ec ed]m.edu - - - - - L. Ca asco Páez e al. Biol.Spo 24(4), 2007 312 in o ma ion abou psychological and soma ic s ess ha a hle es can o expe ience in a compe i i e e o . P olac in (PRL) is a polypep idic ho mone o a single chain wi h 198 aminoacids, s uc u e e y simila o he human g ow h ho mone (hGH). Thei p incipal biological ac ions a e mamo h opic and gonado h opic, al hough no mally se e al ex e nal s imulus can o imp o e he PRL sec e ion. S ess, om psychological o soma ic o igin, is one o his s imulus [1]. As o soma ic s ess induced by exe cise, se e al au ho s ha e ocused hei a en ion in he s udy o PRL esponses o a maximal e o s, unde anae obic ene gy sou ce suppo . In his sense, ises o e 100% om he PRL basal le els ha e been ound a e a p og essi e and maximal e o [7,22]. In o he in es iga ion, he esponse o PRL o an in e al and exhaus i e exe cise was analysed in ained subjec s. Jus a he end o he e o PRL plasma concen a ions ose 230% abo e o basal le els [17]. Also, a impo an inc ease in PRL plasma concen a ions a e an exhaus i e exe cise was ound, al hough cu iously he peak concen a ion was eached 60 min a e exe cise [14]. Howe e , anae obic e o s, o sho du a ion and high in ensi y, like a 60 s o consecu i e e ical jumps, leaded o inc ease PRL plasma concen a ion, e en hough no s a is ical signi icance was ound [5]. On he o he hand, an impo an numbe o in es iga ions o analyse PRL esponse ela ed o ae obic exe cises ha e been de eloped. In his sense, he al e a ions in PRL plasma concen a ion in long dis ance unning (hal ma a hon and ma a hon) ha e been analysed. In his s udies, a signi ican inc ease in PRL concen a ion was obse ed a he end o exe cise [25,30]. In spi e o ha , he e a e da es which o e some con o e sy o he indica ed be o e, since a e o examine PRL plasma concen a ions in 11 male ained a hle es be o e, du ing and a he end o a unning ace o 110 km, no a ia ions we e egis e ed [15]. Al hough wi h some excep ions, e e y hing poin s o ae obic and anae obic exe cises a e p esen ed like a su icien s imulus o induce PRL sec e ion. In ac , a e 60 min o con inuous ae obic exe cise and a e 60 min o in e mi en anae obic exe cise, he PRL plasma concen a ions o nine subjec s who pa icipa ed in his in es iga ion ose signi ican ly abo e he basal le els [18]. Ano he objec i e o pu sue in his ype o in es iga ions is he es ablishmen o a minimal in ensi y o e o om which he PRL esponse and/o elease o PRL occu . In he i s in es iga ions de eloped wi h his aim, he anae obic h eshold was es ablished such as minimal in ensi y necessa y o o induce he PRL esponse [9]. In he nex in es iga ions his in ensi y was loca ed be ween 70 and 80% o - - - - - P olac in and s ess in compe i i e swimming Biol.Spo 24(4), 2007 313 VO2máx, demons a ing ha exe cises o mino in ensi y a e unable o al e PRL plasma le els, o e en can lead o educe hem [12,21]. By he o he hand, and ela ed wi h s ess om psychological sou ce, he e is no e idence ha his ype o s ess would o s imula e he PRL esponse and o cause an inc ease o i s plasma concen a ion. This is ga he ed om he ew s udies in which he esponses o PRL o psychological s ess ela ed o compe i ion ha e been e alua ed [25,29]. A e his p eceden s, he aims o he p esen in es iga ion a e: a) o de e mine he psychological s ess (anxie y) gene a ed by a highly demanding e o –an o icial swimming compe i ion–, and assessing he PRL esponse o his e en , and b) o de e mine he plasma PRL eac i i y o he soma ic s ess induced by his maximal and sho du a ion e o . Ma e ials and Me hods Thi een na ional le el male swimme s, all o whom we e specialis s in swimming dis ances o 100 and 200 m wi h an expe ience o a leas 6 yea s in sys ema ic aining (expe imen al g oup) and en heal hy male s uden s (age- ma ched con ol g oup) ook pa in his s udy. In o med w i en consen was ob ained om all pa icipan s, and he p ojec was app o ed by he e hical commi ee o he Uni e si y o G anada. Gene al and an h opome ic cha ac e is ics o he subjec s a e p esen ed in Table 1. Table 1 Subjec cha ac e is ics Age (y ) Heigh (cm) Weigh (kg) BMI (kg/m2) Body a (%) Expe imen al 18.62 ±0.78 174.95 ±1.80 65.11 ±2.14 21.28 ±0.66 10.75 ±1.00 Con ol 19.10 ±0.82 171.55 ±2.24 74.07 ±4.19 25.09 ±1.15** 21.59 ±1.93*** Da a ep esen means ± SEM **p≤0.01, ***p≤0.001 o Mann-Whi ney es compa ing expe imen al and con ol g oups - - - - - L. Ca asco Páez e al. Biol.Spo 24(4), 2007 314 The swimme s unde wen h ee expe imen al ials. In he i s ial, he swimme s and he con ol g oup, we e es ed in basal condi ions (subjec s we e asked o abs ain om s enuous physical ac i i y o a leas 24 h and o as o 8 h be o e es ing). Upon a i al o he labo a o y, an h opome ical and body composi ion pa ame e s: heigh , weigh , body mass index (BMI), and body a pe cen age (bioelec ic impedance, OMRON BF300 analyse ) we e egis e ed, and a blood sample (10 mL) was ob ained om he an ecubi al ein. Subsequen ly, all subjec s comple ed he S a e - T ai Anxie y In en o y (STAI) [28]. One week la e , a app oxima ely he same ime o day (be ween 8:30 and 10:00 am), in he same es ing and as ing condi ions o he i s ial, he swimme s pa icipa ed in an o icial swimming compe i ion. Be o e compe i ion, and a e 10 min. o es in he swimming pool, a blood sample (10 mL) was ob ained om swimme s, and hey comple ed he STAI ques ionnai e (s a e e sion). This was ollowed by a s anda d wa m-up (20 min. easy swimming). Immedia ely a e he wa m-up pe iod, he swimme s compe ed in hei espec i e 100m ees yle hea s. Time o comple e his dis ance was he mean o ha egis e ed by wo o icial imekeepe s. Immedia ely a e each hea (1-2 min. pos -exe cise) he swimme s we e subjec ed o ano he blood ex ac ion (10 mL), and comple ing he STAI ques ionnai e (s a e e sion). The en i onmen condi ions egis e ed in he compe i ion we e he ollowing: 27.5º C o wa e empe a u e, 29.4º C o ai empe a u e and 58% o ela i e ai humidi y (simila o i s ial condi ions). Each blood sample was di ided in wo aliquo s o 5 mL (EDTA K2 ubes wi h 50 µl o ap o inin: SIGMA A6279). One o he aliquo s was des ined o haema ological analysis (Coul e JT3 analyse ), and plasma was ob ained om he emaining aliquo . Biochemical pa ame e s measu ed in plasma samples we e: PRL concen a ion (RIA, Radim-Ibé ica. In a-assay a ia ion: 4%; in e -assay a ia ion: 6%), o al p o ein concen a ion (elec opho ome y; Hi achi 737 au oanalyse , Bohe inge -Mannheim) and lac a e concen a ion (enzyma ic de e mina ion and e lec ance pho ome y me hod, Accuspo ®, Roche/Boeh inge -Mannheim). Haemog am (haemoglobin concen a ion and haema oc i alue) was pe o med o calcula e he possible changes in plasma olume (PV) ha could al e he esul s o he biochemical analysis [13]. Mo eo e , he plasma o al p o ein concen a ion was de e mined in o de o co obo a e hese changes in PV. Da a a e exp essed as mean ± s anda d e o o he mean (SEM). Non- pa ame ic me hods we e used in s a is ical analysis. F iedman es was used o compa e he expe imen al ials, and Mann-Whi ney es was used o compa e he a iables be ween he expe imen al and he con ol g oup. Fu he mo e, linea - - - - - P olac in and s ess in compe i i e swimming Biol.Spo 24(4), 2007 315 eg ession analysis was pe o med, and Pea son co ela ion coe icien was calcula ed o de e mine he ela ionship be ween a iables. In all cases, s a is ical signi icance was es ablished a an alpha le el o 0.05. Resul s No signi ican di e ences we e obse ed o plasma PRL and lac a e concen a ion measu ed in basal condi ions be ween he expe imen al and con ol g oups. Simila ly, no signi ican di e ences we e obse ed in STAI sco es egis e ed in basal condi ions be ween g oups (Table 2). Table 2 Plasma PRL and lac a e concen a ions and STAI sco es egis e ed in basal condi ions PRL (ng/mL) Lac ic acid (mmol/L) STAI sco es S a e T ai Expe imen al 4.02±0.53 1.77±0.07 18.46±2.79 21.77±3.02 Con ol 4.36±1.09 1.72±0.07 1.72±0.07 22.10±3.63 Da a ep esen means ± SEM. A signi ican inc ease in plasma PRL concen a ion (p≤0.05) was obse ed in p e-compe i ion compa ed wi h basal condi ions (5.52±0.53 s 4.02±0.53 ng/mL, espec i ely). Howe e , plasma lac a e concen a ion in p e-compe i ion si ua ion was simila o he concen a ion obse ed in basal condi ions (1.89±0.04 s 1.77±0.07 mmol/L, espec i ely) (Fig. 1 and Fig. 2). The STAI sco es in p e- compe i ion si ua ion (24.5±3.1) we e signi ican ly highe han hose egis e ed in basal condi ions (Fig. 3), al hough no s a is ical ela ionship was es ablished be ween PRL plasma concen a ions and p e-compe i i e STAI sco es ( =-0.20; p=0.95). Time o comple e he 100 m ees yle was 61.47±1.98 s. In e es ingly, e en hough he compe i ion was o such a b ie du a ion, one inding o his s udy was he dec ease in PV obse ed a e he e o . This dec ease was 11.42±1.28 % compa ed o p e-compe i ion alues. In i s compu a ion, he haemoglobin concen a ions as well as he haema oc i alues p e- and pos -compe i ion we e conside ed. The dec ease in PV was suppo ed by a s a is ically signi ican inc ease - - - - - L. Ca asco Páez e al. Biol.Spo 24(4), 2007 316 o he plasma o al p o ein concen a ion obse ed immedia ely a e he compe i i e e o (Table 3). We used his indi idual pe cen change o co ec each o he ho monal and biochemical de e mina ions. Table 3 Biochemical pa ame e s and changes in plasma olume O icial compe i ion (100 m ees yle) P e – compe i ion Pos – compe i ion To al plasma p o ein (g/dL) 7.77±0.11 8.55±0.11*** Haemoglobin (g/dL) 15.65±0.22 16.54±0.21 Haema oc i (%) 47.27±0.59 50.68±0.66 PV change (%) - 11.42±1.28 Da a ep esen means ± SEM The PRL esponse o he compe i i e e o p oduced a signi ican inc ease in he ci cula ing le els o his ho mone, eaching mean alues o 10.07±1.59 ng/mL. These alues we e signi ican ly highe han he ones ound in basal condi ions and hose obse ed in he p e-compe i ion si ua ion (Fig. 1). Simila inc eases we e obse ed in plasma lac a e. Mean alues o 9.72±0.53 mmol/L we e egis e ed pos -compe i ion. These alues we e also signi ican ly highe han hose ound in basal condi ions and obse ed be o e he swim (Fig. 2). Howe e , eg ession and co ela ion analyses showed no ela ionship be ween PRL and plasma lac a e concen a ions in pos -compe i ion si ua ion ( =0.02; p=0.95). On he o he hand, he pos -compe i ion anxie y alues (22.7±3.2), we e sligh ly lowe han hose ound be o e he beginning o he compe i i e swimming e o , and sligh ly highe han basal le els. No signi ican di e ences we e obse ed wi h ega d o hese STAI sco es (Fig. 3). A signi ican co ela ion (p=0.04) was ound be ween PRL plasma concen a ions and STAI sco es a e he swim, al hough he alue (0.57) showed a weak ela ionship. - - - - - P olac in and s ess in compe i i e swimming Biol.Spo 24(4), 2007 317 Fig. 1 Swimme s’ plasma PRL concen a ions measu ed in all expe imen al ials. *p≤ 0.05; ***p≤ 0.001 compa ed wi h basal condi ion; ++p≤0.01 compa ed wi h p e- compe i ion ial Fig. 2 Swimme s’ plasma lac a e concen a ions measu ed in all expe imen al ials. ***p≤ 0.001 compa ed wi h basal condi ion; +++p≤ 0.001 compa ed wi h p e- compe i ion ial 0 2 4 6 8 10 12 14 P e- Pos - Basal Compe i ion PRL (ng/mL) * *** ++ 0 2 4 6 8 10 12 P e- Pos - Basal Compe i ion Lac ic acid (mmol/L) *** +++ - - - - - L. Ca asco Páez e al. Biol.Spo 24(4), 2007 318 Fig. 3 Swimme s’ s a e – anxie y le els acco ding o he sco es ob ained in he STAI ques ionnai e in he h ee expe imen al si ua ions. **p≤ 0.01 compa ed wi h basal condi ions Discussion F om a psychosoma ic pe spec i e, he e a e ew si ua ions which can p oduce al e a ions such as hose obse ed when an a hle e has o unde ake a maximal e o in compe i ion. In he esponse o hose al e a ions he endoc ine sys em is p omp ly ac i a ed, and he hypo halamic-pi ui a y-ad enoco ical (HPA) axis plays a key ole in he esponse o s ess, whe he his s ess has a soma ic o a psychological o igin (27). PRL is eleased in o he blood in esponse o di e en ypes o s ess. Fo his eason, i s possible ha he analyses o PRL plasma le els in basal si ua ion can o e lec an adap a ion o s ess induced by swimming aining. PRL plasma concen a ions ob ained in basal condi ions o bo h g oups in his in es iga ion a e wi hin he ange p oposed as no mal e e ence alues o adul s (8) and a e e y simila o hose egis e ed in o he s udies (10). Wi h his esul s, and ake in o accoun ha in a la ge numbe o in es iga ions he PRL basal concen a ions o ained and seden a y subjec s a e e y simila [11,21,25] we concluded ha his ho mone le els a e no use ul o e alua e he adap a ion o ch onic s ess induced by swimming aining. 0 5 10 15 20 25 30 P e- Pos - Basal Compe i ion STAI sco es ** - - - - - P olac in and s ess in compe i i e swimming Biol.Spo 24(4), 2007 319 The mean plasma lac a e alues in basal condi ions a e highe han hose epo ed in o he s udies wi h swimme s [3]. These alues a e, howe e , wi hin he ange desc ibed by he a o emen ioned au ho s (0.9-2.3 mmol/L). Ano he impo an aspec o conside is he possible exis ence o psychological al e a ions (anxie y) in he subjec s e alua ed, since his could be he main igge o he PRL elease. Once he sco es om he STAI ques ionnai e, wi h ega d o ai -anxie y and s a e-anxie y we e analysed, and a e compa ing hem wi h he e e ence scale p o ided by Spielbe ge e al. [28] o he spanish popula ion, we conclude ha he sco es we e close o he mean o his popula ion. Al hough se e al s udies ha e epo ed highe ai - anxie y le els in emale swimme s han in ama eu swimme s and seden a y sex and age ma ched g oups [24], compe i i e swimming p ac ice no seems o ha e an e ec on swimme s e alua ed in he p esen in es iga ion. An impo an PRL esponses in swimming compe i ion we e egis e ed. We ound a signi ican inc ease (40%,p≤0.05) in PRL plasma concen a ion be o e aking pa in he swimming compe i ion compa ed o basal alues. These esul s show how PRL esponded o a si ua ion whe e some deg ee o psychological s ess (anxie y) was gene a ed. An inc ease in he s a e-anxie y sco es compa ed wi h he sco es ob ained in he basal condi ion (p≤0.001) e i ied his esponse. These inc eases in he anxie y le els a e in acco dance wi h hose p e iously epo ed [20], al hough in hese s udies he p e-compe i ion s a e-anxie y le els ound in he swimme s we e highe han he le els we ha e eco ded. Ne e heless, he e is no doub abou he ele ance o he swimming compe i ion analysed in ou in es iga ion since p o oked an impo an ise in swimme ’s anxie y le els. In his sense, he ele ance o compe i ion can be conside ed as a decisi e ac o in his ype o in es iga ions [23]. Ou esul s a e opposed o hose epo ed by se e al au ho s whom no ound PRL esponses o p e-compe i ion anxie y [25,29]. As expec ed, he plasma lac a e alues in he p e-compe i ion si ua ion (samples aken be o e wa ming-up) showed no signi ican di e ences om he basal alues. Immedia ely a e inishing he swimming maximal e o (pos -compe i ion), signi ican inc eases in PRL plasma le els we e egis e ed. These alues we e up o 150% highe han basal concen a ions (p≤ 0.001) and 82% highe han hose ound p e-compe i ion (p≤0.01). This la e pe cen change could indica e he ex en o which he physical (soma ic) e o i sel accoun s o he PRL esponse. Al hough i ha e ound PRL esponses o p og essi e and maximal e o s [10,18,31], ou indings, opposed o hose ob ained in p e ious s udies [5], show an e iden PRL esponse o high-in ensi y, sho - e m anae obic exe cise. - - - - -