(Ca2+ + Mg2+) ATPase activity in kidney basolateral membrane in diabetes: role of atrial natriuretic peptide.
The (Ca2+ + Mg2+) ATPase which serves as a Ca2+ pump in the kidney basolateral membranes is essential to the maintenance of an intracellular Ca2+ concentration optimal for kidney function. Since atrial natriuretic peptide (ANP) is known to participate in the Ca2+ homeostasis mechanism, altered levels of ANP in diabetes may vary the pump activity and consequently the kidney function. In order to examine the modulatory role of ANP on (Ca2+ + Mg2+) ATPase in short- (6 weeks) and long-term (6 months) diabetes, rats were injected with streptozotocin (65 mg/kg body wt, i.v.). At 6 weeks, the plasma ANP was decreased whereas, ANP-receptor binding in the kidney basolateral membrane was increased. In contrast, there was an increased plasma ANP and decreased ANP receptor binding at 6 months. Insulin treatment to diabetic animals normalized these parameters. The (Ca2+ + Mg2+) ATPase activity was unchanged both at 6 weeks and 6 months. Our results demonstrate that the unchanged Ca2+ pump activity in short-term and long-term diabetes serves to maintain the Ca2+ homeostasis in the kidney cells and thus may maintain the hyperfiltration state in diabetes. Unaltered (Ca2+ + Mg2+) ATPase is achieved by the initial up-regulation and subsequent down-regulation of the ANP receptors.
Sahai
A
A
Division of Cardiovascular Sciences, St. Boniface General Hospital Research Centre, Winnipeg, Manitoba, Canada.
Ganguly
P K
PK
D000818:Animals; D009320:Atrial Natriuretic Factor / Q000097:blood / Q000378:metabolism*; D001485:Basement Membrane / Q000201:enzymology; D001667:Binding, Competitive; D001786:Blood Glucose; D000252:Calcium-Transporting ATPases / Q000032:analysis* / Q000502:physiology*; D003921:Diabetes Mellitus, Experimental / Q000201:enzymology* / Q000378:metabolism; D007684:Kidney Tubules / Q000201:enzymology* / Q000648:ultrastructure; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains
D001786:Blood Glucose; D009320:Atrial Natriuretic Factor; D000252:Calcium-Transporting ATPases