Calcitropic effects of recombinant prolactins in Oreochromis mossambicus.
Homologous recombinant tilapia prolactin-188 (PRL-I) and tilapia prolactin-177 (PRL-II) were tested for calcitropic activity in tilapia, Oreochromis mossambicus. Injection of PRL-I and PRL-II (4 injections, 12.5 pmol/g, over an 8-day period) induced hypercalcemia that resulted from an enhanced calcium influx via the gills and a decreased calcium efflux. Both PRLs increased the density of the Ca(2+)-transporting Ca(2+)-adenosinetriphosphatase in a plasma membrane preparation of the branchial epithelium. Dose-response studies (doses tested: 0.75-12.5 pmol/g) demonstrated that PRL-I was roughly twofold more potent than PRL-II in inducing hypercalcemia, in enhancing basal levels of cortisol, and in stimulating opercular ionocyte density. PRL-I and PRL-II were equipotent in stimulating the dermal mucocyte frequency. We conclude that in this species PRL-I and PRL-II have calcitropic effects, and that PRL-I is more potent than PRL-II in this respect. We postulate that PRL has corticotrophic activity in this fish.
Flik
G
G
Department of Animal Physiology, Faculty of Science, University of Nijmegen, The Netherlands.
Rentier-Delrue
F
F
Wendelaar Bonga
S E
SE
D000818:Animals; D002118:Calcium / Q000097:blood / Q000378:metabolism*; D000252:Calcium-Transporting ATPases / Q000378:metabolism; D005880:Gills / Q000378:metabolism; D006854:Hydrocortisone / Q000097:blood; D006934:Hypercalcemia / Q000097:blood; D008297:Male; D009093:Mucus / Q000166:cytology; D011388:Prolactin / Q000494:pharmacology*; D011994:Recombinant Proteins; D012867:Skin / Q000166:cytology; D017210:Tilapia / Q000097:blood* / Q000254:growth & development
D011994:Recombinant Proteins; D011388:Prolactin; D000252:Calcium-Transporting ATPases; D002118:Calcium; D006854:Hydrocortisone