EFFECTS OF BETA-ENDORPHIN AND D-ALANINE2 ENKEPHALINAMIDE ON URINE PRODUCTION AND URINARY ELECTROLYTES IN THE RAT
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1979
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Abstract
The intracerebro-ventricular administration of human .beta.-Endorphin (.beta.-EP, 0.1-3 .mu.g/rat) or D-alanine2 methionine enkephalinamide (D-ala, 0.3-30 .mu.g/rat) caused a dose dependent reduction in urine volume. The oliguria was associated with a decrease in the concentration of Na+ and K+ in the urine of rats previously hydrated by oral administration with 25 ml/kg tap water plus 50 ml/kg 0.5% NaCl. On a molar basis, .beta.-EP proved to be about 5-7 times more potent than D-ala. The effects caused by the peptides were antagonized by simultaneous i.p. administration of 1 mg/kg naloxone. In rats treated chronically with morphine, no cross-tolerance was demonstrated to the antidiuretic effect of .beta.-EP, but clear cross-tolerance was evident to the changes in urine electrolytes induced by .beta.-EP. Morphine and the opiate peptides may share a similar mechanism of action.