BETA-ENDORPHIN IS A KIDNEY TROPHIC HORMONE

Intravenous injection of the opioid peptide β-endorphin stimulated an increase in the activity of renal ornithine decarboxylase in rats. The induction of this enzyme is a marker of the growth response of trophic hormone target tissues. Morphine administration promoted an even greater increase in the enzyme activity, which was blocked by the simultaneous administration of the specific opiate antagonist, naloxone. Although hypophysectomy lowered the basal level of ornithine decarboxylase in the kidney, the trophic response to either opioid administration remained intact. This effect of β-endorphin on the kidney may represent a functional role for the circulating endogenous opioid. © 1979.