Renal Implications of Kappa Opioid Receptor Signaling in Sprague-Dawley Rats

Opioid use for pain management and illicit consumption has been associated with adverse cardiovascular and cardiorenal outcomes. Despite these associations, the mechanisms underlying opioid-induced kidney damage remain poorly understood. Recently, we demonstrated that stimulation of kappa opioid receptors (KOR) is implicated in the aggravation of salt-sensitive hypertension, glomerular injury, and podocyte damage through excessive podocyte calcium influx. This study aims to elucidate the KOR signaling and renal outcomes underlying opioid use in Sprague-Dawley (SD) rats. Here, we employed freshly isolated glomeruli from SD male rats and immortalized human podocyte cell cultures to investigate the role of KORs in podocyte calcium regulation and overall glomerular function. A glomerular permeability assay was used to evaluate the impact of KORs on glomerular filter integrity. Additionally, the long-term effects of KOR activation were assessed in vivo by chronic intravenous infusion of selective KOR agonist BRL 52537 in SD rats. We found that acute application of BRL 52537 resulted in increased plasma membrane ion channel activity in immortalized human podocytes. Significant calcium influx in response to BRL 52537 was detected in podocytes of the isolated SD rat glomeruli. Further, glomerular permeability analysis revealed increased permeability and impaired filter integrity, indicating altered glomerular function. Lastly, prolonged KOR activation in SD rats results in an increase in blood pressure, an elevation of basal calcium levels in podocytes, and albuminuria. In conclusion, this study identifies novel renal physiological mechanisms through which opioid-induced KOR activation contributes to podocyte injury and glomerular damage in SD rats.