title: Administration of adrenomedullin into subfornical organ inhibits Na(+),K(+)-ATPase activity in single proximal renal tubule of rats.
abstract: The present study was designed to investigate the effect of administration of adrenomedullin (ADM) into subfornical organ (SFO) on renal tubular Na(+),K(+)-ATPase activity in rats. Rats under anesthesia were injected with ADM 0.1 mL (20 ng/mL) via an implanted cannula into SFO (n=6). Plasma ADM and serum endogenous digitalis-like factor (EDLF) levels were assayed with radioimmunoassay, and urine samples were collected via a canoula intubated in bladder. Urinary sodium concentration was assayed with flame spectrophotometry. Single proximal renal tubule segments were obtained by hand under stereomicroscope and its Na(+),K(+)-ATPase activity was measured by liquid scintillation counting. In addition, single proximal renal tubule segments from normal rats (n=6) were incubated with serum from animals administered with ADM into SFO, and then the Na(+),K(+)-ATPase activity was determined. The results showed that both urinary volume and sodium excretion amounted to the peak value at 30 min after ADM administration, and sustained a significant high level at 60 min (P<0.01). At 30 min after ADM administration, there was a significant increase in serum EDLF and a decrease in Na(+),K(+)-ATPase activity of proximal tubule (P<0.01, respectively), but not in plasma ADM level. Na(+),K(+)-ATPase activity was decreased significantly in single proximal renal tubule segments from normal rats incubated with serum from rats administered with ADM into SFO (P<0.01). These results suggest that the diuretic and natriuretic responses following administration of ADM into SFO are associated with the inhibition of renal tubule Na(+),K(+)-ATPase activity. The inhibition of renal tubule Na(+),K(+)-ATPase activity is related to the increase in the serum level of EDLF.
authors.affiliation: Department of Physiology, Zunyi Medical College Zhuhai Campus, Zhuhai 519041, China. gy60211@yahoo.com.cn
authors.forename: Yuan
authors.initials: Y
authors.lastname: Gao
authors.forename: Xing-Qi
authors.initials: XQ
authors.lastname: Li
mesh_terms: D053607:Adrenomedullin / Q000494:pharmacology*; D000818:Animals; D007687:Kidney Tubules, Proximal / Q000187:drug effects* / Q000201:enzymology; D051381:Rats; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*; D013356:Subfornical Organ
chemical_list: D053607:Adrenomedullin; D000254:Sodium-Potassium-Exchanging ATPase