THE EFFECT OF PHYTOHEMAGGLUTININ AT DIFFERENT DIETARY CONCENTRATIONS ON THE GROWTH, BODY-COMPOSITION AND PLASMA-INSULIN OF THE RAT

Young growing rats weighing approximately 83 g were fed on diets conta ining kidney bean (Phaseolus vulgar is) lectin (phytohaemagglutinin, P HA) in the range of 0-0.45 g/kg body weight for 10 d to ascertain whet her there was a minimum dose below which the lectin had no significant effect on body and skeletal muscle weights in comparison with pair-fe d lectin-free controls, Averaged over all experiments, PHA doses of le ss than 10 mg/d (0.12 g/kg body weight) reduced body dry weight by 1.1 4 (se 0.25) g when compared with controls, Between 10 and 27 mg/d (0.1 2-0.32 g/kg body weight) a further reduction of 0.64 (se 0.21) g occur red, suggesting a slight but steady decline of body dry weight with in creasing dose, However, above 27 mg/d the depression of growth and cha nges in body composition accelerated, The difference between the propo rtional losses of skeletal muscle and body weight was not significant at doses of PHA below 10 mg/d (0.12 g/kg body weight) but the ratio of these losses rose to 1.5-2.0 at doses above this, The proportional de crease in lipid weight exceeded that of both body and skeletal muscle weights at all lectin doses, suggesting that Lipid catabolism was the first target of the PHA effect, Plasma insulin level was depressed at the PHA dose of 0.02 g/kg body weight at which growth depression and m uscle atrophy were minimal but, contrary to expectations, plasma gluco se levels remained stable over the whole PHA dose range, It appears th at despite a PHA-induced lowering of blood insulin, glucose catabolism is elevated by an unknown, possibly hormonal, compensatory mechanism, Thus, because low insulin levels facilitate the mobilization and cata bolism of Lipids, it may be possible to use low doses of PHA to reduce hyperglycaemia and body fat.