Pressor Effect of Guanidine Salts on the Non-anesthetized Rabbit.

A possible relationship between guanidine intoxication and essential hypertension has been suggested. 1 It was of interest to study the question in non-anesthetized animals. This report contains the results of daily examinations for blood pressure and pulse rate in 12 experiments performed on 5 rabbits provided with a good carotid loop (Van Leersum). The salts used (Eastman Kodak Co.) were methylguanidine nitrate (9 experiments), methylguanidine sulphate (2 experiments), and guanidine nitrate (1 experiment). All the rabbits received 0.1 gm. per kilo of body weight but in different concentrations, 1:10 and 1:20 in distilled water, and 1:20, 1:30 and 1:50 in salt solution (4 and 8 per 1000). The total volume of fluid injected was from 3.7 to 8.2 cc. of distilled water and from 6 to 18 cc. of saline. The weights of the rabbits varied from 2.945 to 4.125 kg. After several weeks of observation, the animals received one of the guanidine salts, injected slowly intravenously (marginal vein of the ear). Blood pressure, pulse rate and general reactions were carefully observed immediately after the injection and daily thereafter.

The behavior of blood pressure and pulse rate, in one of the animals, is shown in Fig. 1. Blood pressure is expressed in mm. Hg. (scale to the left); pulse rate in beats per minute (scale to the right). The space between two vertical lines corresponds to one half day. Blood pressure values are the mean of 10 consecutive readings. After the first injection, A, the blood pressure fell and the pulse rate increased, in marked contrast to their behavior before the injection. This condition lasted 18 days after the injection. At B, another injection of same amount of same salt (8.4 cc. of 1:20 in 4:1000 saline) had a similar effect immediately following the injection, but practically no after effect.