The mode of growth hormone administration is of major importance for the excretion of the major male rat urinary proteins

Male and female urinary proteins were analysed using chromatofocusing. Male rat urine had a higher protein content (measured as UV absorbance), particularly in the pI range 5.0-5.5, where female rat urine seemed to lack UV-absorbing material. The molecular weight of the major male rat urinary protein(s) is approximately 16000 according to sodium dodecylsulphate (SDS)-polyacrylamide gel electrophoresis. The regulation of the major male rat urinary protein(s) (pI 5.3; MRUP) was studied in normal male rats and hypophysectomized rats treated for 1 week with various hormones. Urine was collected during the last day of hormone treatment and analysed by chromatofocusing and SDS-polyacrylamide gel electrophoresis. It was found that estrogen treatment of male rats suppressed the appearance of MRUP. This 'feminizing' effect was also observed following continuous infusion for 1 week of human growth hormone (hGH) or rat growth hormone (rGH) in male rats. Single injections of hGH, however, given once daily for 1 week and supplemented with glucocorticoid, thyroid hormone and androgen had an opposite effect and induced MRUP in hypophysectomized male rats. It is concluded that the mode of administration of GH is of great importance for the effects of the hormone and that continuous, as compared to intermittent, administration of GH may result in suppression or induction, respectively, of major male rat urinary protein(s).