In vivo intestinal absorption of L-leucine is significantly decreased by the presence of lindane (0.3, 0.2 and 0.1 mM) in perfusion solution (in situ lindane treatment) for 5 min. The inhibitory effect is earlier when lindane concentration is higher, and it is irreversible. There are no changes in D-galactose absorption when lindane (0.3 and 0.2 mM) is perfused for 5 min, but a significant decrease in observed if pesticide is perfused for 10 min at 0.3 mM concentration. Subcutaneous lindane treatment at a dose of 68.76 mumol/kg over 7 days does not alter D-galactose and L-leucine absorption. In situ lindane treatment (0.3, 0.2 and 0.1 mM) induces a significant decrease in basolateral (Na(+)-K(+)-ATPase activity. In contrast, systemic lindane treatment (s.c. injection) at doses of 34.38 and 68.76 mumol/kg over 7 days does not alter this enzyme activity, although a significant decrease is observed in rats injected s.c. with 68.76 mumol/kg lindane over 15 days.