Hormone metabolism in the pulmonary circulation

We measured hormonal levels in blood samples from pulmonary and radial arte ries in 117 patients undergoing aorto-coronary by-pass surgery with the aim of investigating the role of the pulmonary vessel endothelium in hormone m etabolism. Insulin and glucagon concentrations were significantly higher in pulmonary artery blood with respect to radial artery blood (73+/-65 vs. 65 +/-47 pmol/l, p<0.005, and 80+/-49 vs. 73+/-51 ng/l, p<0.01, respectively), while no difference was found for growth hormone, prolactin, C peptide, in sulin-like growth factor I, follicle stimulating hormone, luteinizing hormo ne, thyroid stimulating hormone, parathyroid hormone, thyroglobulin, triiod othyronine, thyroxine, free triiodothyronine, and free thyroxine. Moreover, prolactin concentrations were more than twice the normal levels, this bein g an effect of propafol and the opiate fentanyl used for the general anesth esia. Assuming that the arteriovenous differences observed are a marker of peptide hormone degradation, our study has demonstrated that with similar k inetics insulin and glucagon secreted into portal circulation and escaping from hepatic extraction undergo further homeostatic removal of about 9-10 % in the pulmonary circulation before entering the general circulation.