CELL DELETION BY APOPTOSIS DURING REGRESSION OF RAT PAROTID SIALADENOSIS

Enlargement of the rat parotid salivary glands was induced by repeated administration of isoproterenol. Mean wet weights of the treated glan ds increased steadily to 240% of control values. Following withdrawal of the drug, quantitative histological techniques were used to investi gate the balance between hypertrophy, hyperplasia and apoptosis. The v olume occupied by acinar cells relative to the total gland volume toge ther with cytoplasmic\:\nuclear area ratios as measures of hypertrophy increased during the early experimental period. Similarly, serous aci nar cell mitotic counts increased, indicating that hyperplasia had occ urred. Apoptosis was demonstrated at light microscopical level to be t he main mechanism for cell deletion as the glands returned to normal s ize and weight. The results indicate that hyper trophy and hyperplasia of serous acinar cells contribute to isoproterenol-induced sialadenos is. The experimental animal model demonstrates that these proliferativ e changes are completed by 48 h and thereafter are balanced by apoptos is as the glands recover their normal size and weight.