Submitted to: Endocrine Society Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 4/1/2004
Publication Date: 6/16/2004
Citation: Fiorotto, M.L., Lopez, R., Oliver, W.T., Rosenberger, J., Draghia-Akli, R. 2004. Nonplacental growth hormone-releasing hormone (GHRH) is transported from the mother to the fetus in the rat [abstract]. The Endocrine Society's 86th Annual Meeting, June 16-19, 2004, New Orleans, Louisiana. Abstract P3-96, p. 488. Interpretive Summary: Not Required for an Abstract.
Technical Abstract: Background: We demonstrated that administration of a protease-resistant GHRH (HV-GHRH) cDNA to pregnant rats increases pituitary weight, somatotroph and lactotroph numbers, and postnatal growth rate of the offspring (1,2). To study whether these responses might reflect direct fetal or indirect maternal effects on fetal pituitary development and fetal growth, we assessed whether mature GHRH peptide present at physiologic concentrations in maternal plasma can be transferred across the placenta. Methods: HV-GHRH peptide was labeled with 125I, purified by reverse phase HPLC (3), reconstituted in 0.05% BSA in PBS, and the specific radioactivity verified (79 mCi/mg peptide). At 18 days of gestation, pregnant dams (n=6) were administered a priming intravenous dose (50 ng) followed by a constant infusion (10 ng/hr) of the labeled peptide using primed Alzet minipumps. Control dams (n=7) matched for gestational age were sham-operated and injected with vehicle. After 48 hours of infusion, dams were anesthetized, blood was collected, and the uterus was exposed. Individual pups, their placenta, and liver were dissected, weighed, and frozen. Pup stomach contents were aspirated and all samples from a litter were pooled. Tissues were homogenized in 50 mM HEPES/0.1% Triton X-100 buffer containing protease inhibitors; all samples were then extracted into 1 % trifluoroacetic acid and passed over C18-Sep columns. The 125I-HV-GHRH in all eluates was purified by HPLC and the 125I radioactivity associated with each HV-GHRH peak was measured. Maternal plasma IGF-I and GH concentrations were measured by RIA using rat-specific reagents. Results: Intact 125I-labeled HV-GHRH was present in fetal stomach contents (3.6 +/- 0.4 (SE) pg/mL fluid) and was positively correlated (r=0.64; P<0.04) with the concentration of 125I-HV-GHRH (24 +/- 3 pg/mL) in the dams' plasma (normal physiologic range <25-100 pg/mL). Intact 125I-HV-GHRH was isolated also from individual fetal livers (3.3 +/- 0.4 pg/g liver). There were no effects of treatment on dam plasma IGF-I and GH concentrations, average placental weight, fetal weight, fetal liver weight, and litter size. Conclusion: These data demonstrate that GHRH of nonplacental origin, even at physiologic concentrations, can cross the placenta and, therefore, has the potential capacity to directly influence fetal pituitary development and fetal growth.