A PTH/PTHrP receptor antagonist blocks the hypercalcemic response to estradiol-17beta.
Estradiol (E(2)) increases circulating calcium and phosphate levels in fish, thus acting as a hypercalcemic and hyperphosphatemic factor during periods of high calcium requirements, such as during vitellogenesis. Since parathyroid hormone (PTH)-related protein (PTHrP) has been shown to be calciotropic in fish, we hypothesized that the two hormones could be mediating the same process. Sea bream (Sparus auratus) juveniles receiving a single intraperitoneal injection of piscine PTHrP(1-34) showed an elevation in calcium plasma levels within 24 h. In contrast, injections of the PTH/PTHrP receptor antagonist PTHrP(7-34) decreased circulating levels of calcium in the same period. Intraperitoneal implants of estradiol-17beta (E(2); 10 microg/g) evoked significant increases of circulating plasma levels of calcium and phosphorus and a sustained increases of circulating plasma levels of PTHrP. However, a combined treatment of E(2) and PTHrP(7-34) evoked a markedly lower calcium response compared with E(2) alone. We conclude that PTHrP or a related peptide that binds the PTH/PTHrP receptor mediates, at least in part, the hypercalcemic effect of E(2) in calcium and phosphate balance in fish.
Fuentes
Juan
J
Centro de Ciências do Mar, CIMAR-Laboratório Associado, Universidade do Algarve, Campus de Gambelas, 8005-139 Faro, Portugal. jfuentes@ualg.pt
Guerreiro
Pedro M
PM
Modesto
Teresa
T
Rotllant
Josep
J
Canario
Adelino V M
AV
Power
Deborah M
DM
D000818:Animals; D002118:Calcium / Q000097:blood; D004347:Drug Interactions; D004958:Estradiol / Q000097:blood / Q000494:pharmacology*; D006706:Homeostasis / Q000187:drug effects / Q000502:physiology; D006934:Hypercalcemia / Q000139:chemically induced / Q000188:drug therapy* / Q000378:metabolism*; D007274:Injections, Intraperitoneal; D010281:Parathyroid Hormone / Q000037:antagonists & inhibitors* / Q000378:metabolism; D044162:Parathyroid Hormone-Related Protein / Q000494:pharmacology; D010446:Peptide Fragments / Q000494:pharmacology; D010710:Phosphates / Q000097:blood; D011506:Proteins / Q000494:pharmacology; D044168:Receptor, Parathyroid Hormone, Type 1 / Q000037:antagonists & inhibitors* / Q000378:metabolism; D021541:Sea Bream
D010281:Parathyroid Hormone; D044162:Parathyroid Hormone-Related Protein; D010446:Peptide Fragments; D010710:Phosphates; D011506:Proteins; D044168:Receptor, Parathyroid Hormone, Type 1; C054296:parathyroid hormone-related protein (1-34); C064776:parathyroid hormone-related protein (7-34)amide; D004958:Estradiol; D002118:Calcium