In vivo modulation of rat hepatic gamma-glutamyltransferase activity by glucocorticoids.
The gamma-glutamyltransferase (gamma-GT) activity decreased by 50% following adrenalectomy of female rats, in homogenate as well as in a purified plasma membrane preparation from liver. In contrast, such a variation was not found in the kidney. None of 3 other enzyme activities of the plasma membrane, namely 5'-nucleotidase, alkaline phosphatase, and alkaline phosphodiesterase I, was decreased by adrenalectomy. Administration of hydrocortisone (5 mg/100 g body weight) resulted in a 2.6-fold increase in hepatic gamma-GT activity from adrenalectomized rats. The hydrocortisone-mediated stimulation of gamma-GT activity was dose- and time-dependent. The 5'-nucleotidase and leucine aminopeptidase activities were not modified by the hydrocortisone treatment. The activity of gamma-GT was mainly associated with nuclear fractions (nuclei and plasma membranes) obtained from liver homogenates of either control, adrenalectomized or adrenalectomized hydrocortisone-treated animals, and this activity was purified 18-fold in a plasma-membrane preparation as compared to homogenate. These data suggest that adrenalectomy and conversely hydrocortisone treatment modulate specifically the hepatic plasma-membrane gamma-GT activity. This represents one of the first demonstrations of a specific modulation by glucocorticoids of an enzyme activity typical of the plasma membrane.
D000315:Adrenalectomy; D000818:Animals; D002462:Cell Membrane / Q000201:enzymology; D004305:Dose-Response Relationship, Drug; D005260:Female; D006854:Hydrocortisone / Q000494:pharmacology*; D007700:Kinetics; D007931:Leucyl Aminopeptidase / Q000378:metabolism; D008099:Liver / Q000187:drug effects / Q000201:enzymology*; D009708:Nucleotidases / Q000378:metabolism; D011506:Proteins / Q000378:metabolism; D051381:Rats; D005723:gamma-Glutamyltransferase / Q000378:metabolism*
D011506:Proteins; D005723:gamma-Glutamyltransferase; D009708:Nucleotidases; D007931:Leucyl Aminopeptidase; D006854:Hydrocortisone