by Katia Regina Cesar, Eliete Caló Romero, Ana Carolina de Bragança, Roberta Morozetti Blanco, Patrícia Antonia Estima Abreu, Antonio José Magaldi
Leptospirotic renal lesions frequently produce a polyuric form of acute kidney injury with a urinary concentration defect. Our study investigated a possible effect of the glycolipoprotein, (GLPc) extracted from L. interrogans, on vasopressin (Vp) action in the guinea pig inner medullary collecting duct (IMCD). Methods
The osmotic water permeability (Pf µm/s) was measured by the microperfusion in vitro technique. AQP2 protein abundance was determined by Western Blot. Three groups were established for study as follows: Group I, IMCD from normal (ngp, n?=?5) and from leptospirotic guinea-pigs (lgp-infected with L. interrogans serovar Copenhageni, GLPc, n?=?5); Group II, IMCD from normal guinea-pigs in the presence of GLPc (GLPc group, n?=?54); Group III, IMCD from injected animals with GLPc ip (n?=?8). Results
In Group I, Pfs were: ngp- 61.8±22.1 and lgp- 8.8±12.4, p<0.01 and the urinary osmolalities were: lgp-735±64 mOsm/Kg and ngp- 1,632±120 mOsm/Kg. The lgp BUN was higher (176±36 mg%) than the ngp (56±9 mg%). In Group II, the Pf was measured under GLPc (250 µg/ml) applied directly to the bath solution of the microperfused normal guinea-pig IMCDs. GLPc blocked Vp (200 pg/ml,n?=?5) action, did not block cAMP (10-4 M,) and Forskolin (Fors- 10-9 M) action, but partially blocked Cholera Toxin (ChT- 10-9 M) action. GLP from L.biflexa serovar patoc (GLPp, non pathogenic, 250 µg) did not alter Vp action. In Group III, GLPc (250 µg) injected intraperitoneally produced a decrease of about 20% in IMCD Aquaporin 2 expression. Conclusion
The IMCD Pf decrease caused by GLP is evidence, at least in part, towards explaining the urinary concentrating incapacity observed in infected guinea-pigs.