Effect of a prolactin pharmacological stimulant (sulpiride) and suppressant (bromocriptine) on heat shock protein 70 expression in silver sea bream, Sparus sarba

Heat shock protein 70 (HSP70) expression was assessed in hepatic tissue of silver sea bream, Sparus sarba. Using a combination of reverse transcriptio n and PCR we have cloned a 794 base pair HSP70 cDNA fragment. This clone hy bridized to a 2.3kb HSP70 mRNA transcript which was elevated 2.5 fold after acute heat shock exposure. Cold shock however, had no effect on HSP70 expr ession. In order to study the effect of prolactin on silver sea bream hepat ic HSP70, groups of fish received either ovine prolactin (oPRL), sulpiride or bromocriptine, daily, over a seven day period. Treatment with oPRL and s ulpiride resulted in a reduction in the relative abundance of hepatic HSP70 mRNA by 48 and 52%, respectively. Also hepatic HSP70 levels were reduced b y 69 and 46% (as determined by immunoblotting) after oPRL and sulpiride adm inistration, respectively. The administration of bromocriptine significantl y increased both HSP70 mRNA and protein levels by 197 and 240%, respectivel y. The data from this study provides strong support for the importance of p rolactin in regulating HSP70 expression in silver sea bream.