Effects of nerve growth factor on cyclocytidine-induced growth responses of sympathectomized parotid or parotid of partially desalivated rat.

Cyclocytidine (CC), a potent antitumor agent, caused a 2.4- to 3.9-fold increase in [3H]thymidine uptake of rat parotid gland after 3 days of daily administration of the CC in a dose of 500 mg/kg body weight. Gland weight also was increased. Ablation of the submandibular-sublingual glands prior to initiation of the CC regimen prevented the usual CC-induced increase in [3H]thymidine uptake but this inhibition was partially reversed when nerve growth factor (NGF) was administered with the CC; values for [3H]thymidine uptake into parotid DNA were 81, 54, and 73% of those of glands of intact CC-treated rats. Submandibular gland ablation did not prevent the usual CC-induced increase in parotid size, and administration of NGF had no effect. Sympathectomy of the salivary glands also inhibited the thymidine increase in parotid gland usually induced by CC but in addition it also inhibited the usual CC-induced increase in gland weight. NGF, however, failed to reverse the effects of sympathectomy on [3H]thymidine uptake or gland size: both remained at the same level observed in sympathectomized parotid not given NGF.