title: Consequences of cerebroventricular insulin injection on renal sodium handling in rats: effect of inhibition of central nitric oxide synthase.
abstract: In the present study, we investigated the effects of acute intracerebroventricular (icv) insulin administration on central mechanisms regulating urinary sodium excretion in simultaneously centrally NG-nitro-L-arginine methylester (L-NAME)-injected unanesthetized rats. Male Wistar-Hannover rats were randomly assigned to one of five groups: a) icv 0.15 M NaCl-injected rats (control, N = 10), b) icv dose-response (1.26, 12.6 and 126 ng/3 microL) insulin-injected rats (N = 10), c) rats icv injected with 60 microg L-NAME in combination with NaCl (N = 10) or d) with insulin (N = 10), and e) subcutaneously insulin-injected rats (N = 5). Centrally administered insulin produced an increase in urinary output of sodium (NaCl: 855.6 +/- 85.1 Delta%/min; 126 ng insulin: 2055 +/- 310.6 Delta%/min; P = 0.005) and potassium (NaCl: 460.4 +/- 100 Delta%/min; 126 ng insulin: 669.2 +/- 60.8 Delta%/min; P = 0.025). The urinary sodium excretion response to icv 126 ng insulin microinjection was significantly attenuated by combined administration of L-NAME (126 ng insulin: 1935 +/- 258.3 Delta%/min; L-NAME + 126 ng insulin: 582.3 +/- 69.6 Delta%/min; P = 0.01). Insulin-induced natriuresis occurred by increasing post-proximal sodium excretion, despite an unchanged glomerular filtration rate. Although the rationale for decreased urinary sodium excretion induced by combined icv L-NAME and insulin administration is unknown, it is tempting to suggest that perhaps one of the efferent signals triggered by insulin in the CNS may be nitrergic in nature.
authors.affiliation: Faculdade de Medicina, Universidade Federal de Uberlândia, Uberlândia, MG, Brasil.
authors.forename: P C
authors.initials: PC
authors.lastname: Oliveira
authors.forename: J B
authors.initials: JB
authors.lastname: Michelotto
authors.forename: A
authors.initials: A
authors.lastname: Zapparoli
authors.forename: P A
authors.initials: PA
authors.lastname: Boer
authors.forename: J A R
authors.initials: JA
authors.lastname: Gontijo
mesh_terms: D000818:Animals; D001921:Brain / Q000201:enzymology*; D007276:Injections, Intraventricular; D007328:Insulin / Q000008:administration & dosage / Q000494:pharmacology*; D008297:Male; D008845:Microinjections; D019331:NG-Nitroarginine Methyl Ester / Q000008:administration & dosage; D009318:Natriuresis / Q000187:drug effects*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors*; D011897:Random Allocation; D051381:Rats; D017208:Rats, Wistar
chemical_list: D007328:Insulin; D019001:Nitric Oxide Synthase; D019331:NG-Nitroarginine Methyl Ester