I. Ishaaya, J. Casida
Aug 1, 1975
Citations
0
Influential Citations
28
Citations
Journal
Pesticide Biochemistry and Physiology
Abstract
Abstract The potency of dietary phenyltin compounds in inhibiting the growth of first and fourth instar Tribolium confusum L. larvae and the gut proteolytic activity of fourth instar larvae decreases in the order of triphenyltin chloride (Ph 3 SnCl) ⪢ diphenyltin dichloride (Ph 2 SnCl 2 ) ⪢ phenyltin trichloride or tetraphenyltin. The growth retardation, which prolongs the larval stage without affecting pupation or emergence, may result from an antifeeding effect involving gut protease inhibition by Ph 3 Sn + and Ph 2 Sn 2+ . Gut amylase and invertase activities are less sensitive than the protease activity to in vivo inhibition. Under in vitro conditions, relatively high concentrations of Ph 3 SnCl and Ph 2 SnCl 2 are required for inhibition, the order of enzyme sensitivity is protease > amylase > invertase, and Ph 2 SnCl 2 is more potent than Ph 3 SnCl. Proteins such as casein, albumin and hemoglobin, but not carbohydrates such as starch and sucrose bind Ph 3 Sn + so it is inaccessible for inhibition of digestive enzymes. The level of Ph 3 Sn + inhibiting gut protease in vivo is far below that necessary for in vitro inhibition of this enzyme activity. It is speculated that the in vivo inhibitory effects of Ph 3 Sn + and Ph 2 Sn 2+ on digestive enzymes may result from binding to the enzyme protein, its zymogen or to other proteins involved in production of the digestive enzymes.