Letter: are rauwolfia alkaloids carcinogenic?

Effect of reserpine on cell proliferation in the developing rat bran: a biochemical study

Reserpine, a well-known CNS depressant which depletes central monoamine stores, was found to produce in the brains of 11-day-old rats a severe depression in cell proliferation in terms of the rate of [3H]thymidine incorporation into DNA. The effect was studied in detail 12 h after ther administration of the drug (2.5 mg/kg, s.c.) when the rate of in vivo DNA synthesis in the forebrain was about one-third of control: the decrease was less marked in the cerebellum (rate about two-thirds of control). It was possible to exclude side effects of the drug, such as restricted food intake, hypothermia and an elevation of the level of blood corticosteroids being responsible for the reduction of [3H]thymidine incorporation into DNA. Kinetic studies showed that reserpine had no marked effect on the entry of [3H]thymidine from blood to brain, but it caused some retardation in the rate of [3H]thymidine conversion into [3H]thymidine nucleotides. Nevertheless, the severe depression of DNA labelling was evident even after correcting the values on the basis of [3H]thymidine nucleotide concentrations. In contrast to these effects, thymidine kinase activity was normal in the brain of reserpine-treated animals.

Effects of reserpine, epidermal growth factor, and cyclic nucleotide modulators on epidermal mitosis

The mouse ear G2 mitosis assay was modified for the screening of potential antimitotic agents. An inhibitory adrenergic influence, which maintains mitotic rate at a normally low level, was removed by pretreatment of mice with reserpine. This depletes endogenous catecholamines, produces a state of enhanced mitotic activity, and makes the epidermal cells particularly sensitive to mitotic inhibition by agents which elevate the levels of cyclic AMP. Isoproterenol [IC 50 approximately 1 X 10(-9) M], prostaglandins, dibutyryl cyclic AMP [IC 50 approximately 2 X 10(-5) M], papaverine, theophylline and 5' AMP were inhibitory in the assay, whereas dibutyryl cyclic GMP and the cholinergic stimulator carbamylcholine either stimulated or had no effect on mitosis. Epidermal growth factor was employed as an alternate means of stimulating cell division. Skin fron newborn mice or rats pretreated with this substance had increased epidermal mitotic activity which was inhibited cyclic AMP elevators.

Rauwolfia derivatives and breast cancer. A case/control study in Olmsted County, Minnesota

In response to three reports of an association between rauwolfia derivatives and breast cancer, a case/control study was undertaken in Olmsted County, Minnesota. Comparison of a cohort of women with breast cancer to an age-match cohort of women with cholelithiasis failed to show any meaningful differences in the two groups except with respect to a history of hypertension. The rates of use of rauwolfia derivatives by hypertensive cases and controls were identical--which, along with other considerations, leads to the conclusion that an association between the use of rauwolfia derivatives and breast cancer is unlikely.