Use of antisense techniques in rat renal medulla

The experiments outlined in this chapter utilized a novel infusion technique to deliver an antisense oligonucleotide (and an enzyme inhibitor) directly into the renal medullary interstitial space of conscious rats. Antisense treatment led to a selective decrease in nNOS protein and reduced total NOS enzymatic activity in the renal medulla of the infused rats while three other gene products found in the renal medulla (iNOS, eNOS, and β- actin) were unaltered. Physiological studies in rats demonstrated that infusion of the antisense oligonucleotide into the renal medullary interstitial space increased mean arterial pressure. The increase in blood pressure was dependent on the sodium intake of the rats, was not mimicked when a scrambled oligonucleotide was infused, and was reversible when the antisense infusion was stopped. To confirm the functional data obtained with the antisense oligonucleotide, renal medullary interstitial infusion of the nNOS enzyme inhibitor 7-NI was also shown to lead to a similar increase in arterial pressure and decrease in total NOS activity in the renal medulla. Together, the antisense oligonucleotide, the enzyme inhibitor, and the interstitial infusion technique were used to demonstrate that nNOS found in the renal medulla is important in the chronic regulation of arterial pressure. The experiments summarized in this chapter outline a strategy that can potentially be used to examine the functional effects of many different proteins in this region of the body. Through the use of antisense oligonucleotides and other pharmacological agents, we can hope to gain a more comprehensive understanding of the factors that control renal medullary tubular and vascular function and consequently fluid and electrolyte homeostasis and blood pressure.