Secretion of medullipin I by the kidney requires oxygen.
OBJECTIVE
To test the hypothesis that the secretion of medullipin I by the kidney involves an oxidative step.


METHODS
Medullipin I is secreted by kidney renomedullary interstitial cells and is converted to medullipin II by the liver. Medullipin I can be derived from the kidney in the renal venous effluent by perfusing normal rat kidneys with 95% O2- 5% CO2 at an elevated pressure (180 mmHg). To evaluate whether the secretion of medullipin I involves an oxidative step normal rat kidneys were perfused at an elevated pressure in the presence of O2, in the absence of O2 and after treatment of the kidneys with a powerful antioxidant.


METHODS
Normal rat kidneys were perfused with 5% albumin bubbled with O2-CO2 at 180 mmHg. This was the control procedure for each of the three approaches. In approach (1), the kidneys were perfused with 5% albumin bubbled with N2. In approach (2), the kidneys were perfused with 'blood' treated with carbon monoxide. In approach (3), the kidneys were treated with the antioxidant butylated hydroxytoluene then perfused with 5% albumin bubbled with O2-CO2. Each perfusate was tested for medullipin I activity by rapid intravenous injection into the SHR.


RESULTS
All three approaches, which exclude the action of molecular O2, prevented the secretion of medullipin I by the kidneys.


CONCLUSIONS
The secretion of medullipin I by the kidneys involves an oxidative step.
Muirhead
E E
EE
Department of Pathology, University of Tennessee, Memphis 38163.
Brooks
B
B
Byers
L W
LW
D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D066298:In Vitro Techniques; D007679:Kidney Medulla / Q000187:drug effects / Q000378:metabolism*; D050356:Lipid Metabolism; D008055:Lipids / Q000494:pharmacology; D010084:Oxidation-Reduction; D051381:Rats; D011918:Rats, Inbred SHR; D017207:Rats, Sprague-Dawley; D012016:Reference Values
D008055:Lipids; C050534:medullipin I