Proc. West. Pharmacol. Soc. 45: 99-100 (2002) Glucose Transport Across Renal Brush Border Membrane of Renovascular Hypertensive Rats ROCÍO BAUTISTA 1 , FLAVÍO MARTÍNEZ 3 , HILDA VARGAS 1 , AMELIA RÍOS 2 & BRUNO ESCALANTE 1 * Department of 1 Molecular Biomedicine and 2 Department of Pathology, Centro de Investigación y de Estudios Avanzados del IPN, México D.F; 3 Department of Pharmacology, Facultad de Medicina de la UASLP, México *e-mail: bescalan@mail.cinvestav.mx Considerable evidence suggests that hypertension may be associated with altered cellular ion transport. Several transport systems are affected in hypertension, including the inhibition of active Na + transport [1,2], increased pas- sive membrane permeability for Na + [3] and stimulation of the Na + -H + exchanger [4-6], H + -ATPase [6], and Na + - glucose cotransporter [7]. Recent studies in proximal tu- bule cells demonstrated that H + -ATPase, Na + -H + ex- change, Na + /HCO 3 cotransporter and Na + /K + -ATPase are activated by angiotensin II [8]. Furthermore, reabsorption in response to dopamine is diminished and in response to angiotensin II is enhanced in the proximal tubule in spon- taneously hypertensive rats [9,10]. In the present study, we have examined the activity of the Na + -glucose cotransporter, in renal brush-border mem- brane vesicles (BBMV) isolated from angiotensin II- dependent renovascular hypertensive rats. METHODS: Aortic coarctation. Aortic coarctation was performed according to published procedures [11]. We used male Wistar rats (weighing 300- 350 g), the animals being divided into the following groups (n=50): sham-operated (SO) and aortic coarctation (AC). Systolic blood pres- sure was measured 21 days after of surgery. Brush-border membrane vesicle preparation. After blood pres- sure measurements, the right kidney outer cortex was removed to iso- late BBMV [12]. Protein content was determined according to the Bradford method [13]. The purity of the prepared membrane vesicles was evaluated by measuring, in the homogenate and the final vesicles, the specific activity of alkaline phosphatase, leucine aminopeptidase (brush-border marker enzyme) and Na + /K + -ATPase (basolateral marker enzyme) [12]. Enrichments of the preparations was calculated by divid- ing enzymatic activity of the BBMV/homogenate, purity was achieved when enrichment factor >> 1. Transport experiments. Glucose transport was determined at room temperature by a rapid filtration technique [14]. Statistical analysis. All results are expressed as mean ± SEM. Comparisons were made with one-way ANOVA. A value of p<0.05 was considered statistically significant. RESULTS: Systolic blood pressure was 120 ± 3 and 155 ± 3 mm Hg in sham-operated rats (SO) and aortic con- stricted rats (AC), respectively. Table 1 show that brush- border marker enzymes was enriched 11-13 fold in BBMV from SO and AC compared to the initial homoge- nate. Specific activities and enrichments of the brush- border marker enzymes were not statistically different between preparations of BBMV obtained, indicating that these preparations were suitable for comparative studies of solute transport rates. In contrast, enrichments and spe- cific activity of Na + /K + -ATPase in BBMV was low, indi- cating very little contamination with basolateral mem- brane. Figure 1 shows that in BBMV of animals with aortic coartaction the uptake of glucose increased from 257 ± 30 to 348 ± 25 pmol/mg protein/min. Figure 1. Uptake of glucose by brush-border membrane vesicles (BBMV) from isolated kidney cortex of sham-operated and aortic coartacted rats. Each bar represent the mean ± SEM, n= 5, *p<0.05. DISCUSSION: It has been suggested that ion resorption may contribute to the development of hypertension. In the present study, we demonstrate that in BBMV prepared from renovascular hypertensive rats, glucose transport was increased. This increase in the activity of transporter is not due to variations in vesicle preparations, because the purification, as measured from the enrichment of alka- line phosphatase and leucine aminopeptidase, were simi- lar for all experimental groups. 99