CALCIUM-CHANNEL BLOCKERS MODIFY JEJUNAL UPTAKE OF D-GALACTOSE IN RABBITS

Calcium channel blockers modify the intestinal uptake of lipids, This study was undertaken to test the hypothesis that two different types o f calcium channel blockers influence the uptake of D-galactose, a suga r absorbed by the sodium-dependent glucose transporter (SGLT(1)) in th e intestinal brush border membrane, Nisoldipine (1 mg/kg/day) or verap amil (4 mg/kg/day) were given by mouth to New Zealand white rabbits fo r three weeks, and then the rates of uptake of varying concentrations (2-64 mM) of galactose were examined in an in vitro preparation of jej unum using the incorporation of C-14-labeled substrate into intact tis sue segments, The maximal transport capacities (V-max) for D-galactose were increased in animals given nisoldipine or verapamil, as compared to controls. The value of the apparent Michaelis constant (K-m) for D-galactose was higher with nisoldipine group and lower with verapamil , than in controls. The apparent passive permeability (P-d) of D-gala ctose was estimated from the uptake of L-glucose: P-d was lower with misoldipine and higher with verapamil, as compared to controls, The ef fect of these drugs on sugar uptake is not due to differences in the a nimals' food intake, body weight gain, or mucosal surface area. Thus, the two different classes of calcium channel blockers, the dihydropyri dine nisoldipine and the phenylalkylamine verapamil, have different ef fects on the K-m and P-d*, but not on the V-max of D-galactose uptake .