Displacement of 3H-EKC binding by opioids in rat kidney: a correlate to diuretic activity

Multiple opioid binding sites have been documented in brain tissue. In this study we report on the presence of binding sites for the opioid ethylketocyclazocine (EKC) in a membrane fraction of rat kidney. Binding appeared to be selective in that opioids varied markedly in their capacities to displace 3H-EKC. Correlating with the capacity of an opioid to displace 3H-EKC was the ability to produce diuresis. Although our studies cannot assign a particular physiological or pharmacological role for the renal EKC binding sites, binding studies of this nature may, nonetheless, be a means by which diuretic activity of opioids can be predicted.