T.B. Ng

Metabolic effects of bovine growth hormone in the tilapia Oreochromis mossambicus

1. Bovine growth hormone (bGH) was injected into tilapia intramuscularly at a dose of 50 micrograms/100 g/day for a total of five injections. Control fish received saline instead. 2. The serum concentrations of amino acid and glucose were significantly higher and hepatic glycogen concentration and glycogen synthetase activity significantly lower in the bGH-treated fish than those in the control fish. 3. The serum concentrations of protein, lipid and cholesterol, and the hepatic concentrations of protein and lipid, remained unaltered after bGH treatment. 4. The results suggest that bGH exerts anti-insulin effects in tilapia.

Growth hormone binding sites in tilapia (Oreochromis mossambicus) liver

125I-labeled bovine and tilapia growth hormones were used to assess the presence of growth hormone receptors in membranes prepared from tissues of the tilapia Oreochromis mossambicus. The highest level of specific binding was detected in liver membranes from animals of both sexes and the binding was protein-dependent. Tilapia growth hormone, bovine growth hormone, and ovine prolactin, but not tilapia prolactin, potently inhibited the hepatic binding of 125I-labeled bovine growth hormone. Scatchard analysis of the 125I-labeled bovine growth hormone binding data revealed a Bmax (maximum binding) value of 180 fmol/mg protein and a Kd (dissociation constant) value of 13 nM. Tilapia growth hormone potently inhibited hepatic binding of 125I-labeled tilapia growth hormone. Scatchard analysis revealed a single class of binding sites with Bmax and Kd values of 390 fmol/mg protein and 2.5 nM, respectively. Bovine growth hormone and ovine prolactin were less potent while tilapia prolactin was inactive in inhibiting hepatic 125I-labeled tilapia growth hormone binding.

Presence of prolactin receptors in eel liver and carp kidney and growth hormone receptors in eel liver

1. 125I-labelled ovine prolactin and bovine growth hormone were used to test for the presence of prolactin and growth hormone receptors in membrane prepared from tissues of the white eel Anguilla japonica, the carp Ctenopharynogodon idellus and the ricefield eel Monopterus albus. 2. High levels of specific 125I-labelled ovine prolactin binding were found in white eel liver membranes and carp kidney membranes. 3. High levels of specific 125I-labelled bovine growth hormone binding were detected in white eel liver membranes. 4. Tissues of the ricefield eel did not bind 125I-labelled ovine prolactin or bovine growth hormone. 5. The results suggest the presence of prolactin receptors in white eel liver and carp kidney membranes and growth hormone receptors in white eel liver membranes.

Presence of prolactin receptors in kidney and large intestine of the snake Ptyas mucosa

125I-labeled ovine prolactin was used to test for the presence of prolactin receptors in membranes prepared from tissues of the common rat snake Ptyas mucosa. High levels of specific binding were found in kidney and large intestine membranes prepared from snakes of both sexes. The binding was time, temperature, and protein dependent. The presence of Ca2+ in the incubation medium enhanced the binding, with optimal concentrations at 10-20 mM. Specificity of binding was established by employing different hormones as the displacing species in the radioreceptor assay. The results suggested the presence of lactogenic receptors in snake kidney and large intestine membranes. Scatchard analysis of the binding data indicated the presence of a single class of binding sites in snake kidney membranes with a dissociation constant of 0.83 nM. The present study is the first report of the presence of prolactin receptors in snake kidney and large intestine membranes.

Growth hormone binding sites are present in tissues of the porcupine Hystrix hodgesoni, the snakehead Channa maculata and the winter flounder Pleuronectes americanus but not in those of the lamprey Petromyzon marinus

Abstract 1. 1. Various tissues of the porcupine Hystrix hodgesoni including liver, intestine, stomach, spleen, kidney, brain and lung were examined for the presence of growth hormone binding sites. 2. 2. Membranes were prepared from the aforementioned tissues and tested for binding to 125I-bovine growth hormone (125I-bGH). 3. 3. Porcupine kidney membranes yielded 1.3 and 2.7% specific binding when tested at 1000 and 2500 μg protein, respectively. Porcupine liver membranes demonstrated approximately 1% specific binding at 3000 μg protein. The other tissues gave low specific binding. The results indicate that porcupine kidney contained binding sites for growth hormone. 4. 4. Various tissues of two teleosts, the snakehead Channa maculata and the winter founder Pleuronectes americanus, were similarly processed and tested for binding to 125I-bGH. It was found that among the different tissues studied, the liver membranes of Channa maculata and the gonad membranes of Pleuronectes americanus gave the highest specific binding of 125I-bGH. 5. 5. Liver and intestine membranes of the lamprey Petromyzon marinus did not bind 125I-bGH.

Study on the effects of estradiol-17β, estrone, catechol estrogens, [D-Ala6]-luteinizing hormone releasing hormone and human chorionic gonadotropin on serum levels of lipids and vitellogenin in the immature duckling (Anas platyrhynchos)

Abstract 1. 1. The effects of administration of estradiol-17β (E2), estrone (E1), catechol estrogens, [ d -Ala6]-luteinizing hormone releasing hormone (LHRH) and human chorionic gonadotropin (HCG) on serum levels of vitellogenin and lipids were examined in immature ducklings. 2. 2. E2 brought about an elevation in serum levels of total lipid, triglyceride, cholesterol and vitellogenin. 3. 3. Treatment with both LHRH and E2 resulted in an increase in serum levels of total lipid, triglyceride, cholesterol and vitellogenin. 4. 4. Treatment with LHRH alone, HCG, E1 or catechol estrogen failed to exert any effect on serum lipid or vitellogenin level. 5. 5. The results indicate that, of the various hormones examined including estrogens, LHRH and HCG, only E2 was able to affect serum lipid and vitellogenin concentrations in the duckling.