In vivo and in vitro effects of prolactin and growth hormone on lipid metabolism in a teleost, Anabas testudineus (Bloch)

Prolactin (PRL) has an important role in the regulation of water and electr olyte homeostasis in teleosts. The present study was designed to evaluate t he role of PRL and GH on malic enzyme (ME), glucose-6-phosphate dehydrogena se (G6PDH) and isocitrate dehydrogenase (ICDH) in Anabas testudineus. Ovine prolactin significantly inhibited ME, G6PDH and ICDH activities when admin istered in vivo compared to vehicle treated controls. In vivo administratio n of PRL reversed the action of bromocryptine on enzyme activities. Ovine g rowth hormone in vivo also modified the effect of bromocryptine but not to the level of prolactin. Combined action of PRL + GH in vivo was most effect ive in keeping the enzyme activities at normal level after bromocryptine tr eatment. Prolactin in vitro also reversed the action of bromocryptine on en zyme activities, while GH in vitro failed to do so. Hence, prolactin seems to have an inhibitory effect on lipid metabolism in this teleost. Combined action of PRL + GH is more prominent in in vivo conditions at low PRL level s. Dopaminergic pathways may be involved in the control of prolactin and to some extent on growth hormone secretion. (C) 2001 Elsevier Science Inc. Al l rights reserved.