Evidence for direct effect of growth hormone on capillary basement membrane thickness.

In order to investigate the direct effect of growth hormone on the capillary basement membrane thickness (CBMT), we performed, in normal and diabetic rats, ultrastructural morphometric studies on the capillaries of the skin loci where the intracutaneous injections of physiologic saline and human growth hormone (HGH) in various concentrations had been repeated daily for 28 days. In the normal group, the injection (0.1 ml daily) of HGH solutions in concentrations of 0.5 micrograms/ml and 2 micrograms/ml did not significantly alter the CBMT, and only at the concentration of 10 micrograms/ml, HGH significantly (p less than 0.001) increased the CBMT. In the diabetic group, however, the injection of any of the HGH solutions significantly (p less than 0.001 approximately 0.05) increased the CBMT. In another diabetic rat series, HGH, human albumin, human menopausal gonadotropin and human globulin (each in a concentration of 10 micrograms/ml) were repeatedly injected into four separate skin portions for 28 days, and it was found that the net increase in CBMT was most striking in the HGH-treated portion. These data demonstrated the direct and specific effect of HGH on CBMT.