Effects of glutaraldehyde fixation on renal tubular function

Abstract

Using the in vitro microperfusion technique on isolated rat papillary collecting duct (PCD), we examined whether the glutaraldehyde-fixation method can be also applied to the mammalian collecting duct for preservation of the vasopressin-stimulated water and urea transport. Arginine vasopressin (AVP) at 10⁻⁹ mol/l increased diffusional water permeability (P _dw) from 101.9±10.76 to 283.3±16.67×10⁻⁷ cm² s⁻¹ (n=8,P<0.01) and urea permeability (P _urea) from 30.3±2.24 to 83.5±7.80×10⁻⁷ cm² s⁻¹ (n=8,P<0.01). Both parameters remained elevated after fixation with 0.1 mol/l glutaraldehyde even in the absence of AVP, with the values being 265.0±14.47 and 74.5±7.15×10⁻⁷ cm² s⁻¹, respectively. Glutaraldehyde fixation did not affect the basal levels ofP _dw orP _urea. Phloretin at 2.5×10⁻⁴ mol/l decreased glutaraldehyde-fixed AVP-stimulatedP _urea from 79.0±7.96 to 29.7±3.66×10⁻⁷ cm² s⁻¹ (n=4,P<0.01) and from 73.2±7.05 to 38.7±3.53×10⁻⁷ cm² s⁻¹ (n=4,P<0.01) when the drug was added to the lumen or to the bath, respectively. Phloretin also decreased glutaraldehyde-fixed non-stimulatedP _urea by 25–40%. However, this drug did not affect glutaraldehyde-fixedP _dw. These findings indicate that the glutaraldehyde fixation method can be applied to mammalian collecting tubules for studying vasopressin stimulatedP _dw andP _urea.P _urea fixed by glutaraldehyde is functionally flexible and may be distinct from the water pathway.