[Studies on the combined effect of pesticide mixtures belonging to different chemical groups on calcium absorption in rat intestine. Part II. Chlorfenvinphos and cypermethrin].

In male Wistar rats study was made of the effect of multiple treatment (14 days) with single pesticides (chlorfenvinphos and cypermethrin) and with their mixture on intestinal calcium absorption. Pesticides were administered intragastrically through a stomach tube in a daily dose corresponding to 5% of LD50; in the case of the pesticide mixture, 5% of LD50 of each component were administered. Calcium uptake (active and passive) by duodenal sections were determined by the method of Papworth and Patrick, modified by the present authors. It was found that under the applied experimental conditions chlorfenvinphos influences the active transport of calcium, causing an increase in the values of the constants Jm (maximal transport rate) and Kt (affinity of calcium to carrier), whereas it inhibits the passive transport. Similar changes were displayed by rats exposed to cypermethrin. On the other hand, combined administration of both pesticides led to a lack of changes in the efficiency of active transport and to impairment of passive transport, as compared with control.