Search

In order to evaluate the effects in adults of different doses of ACTH 1-17 on the cortisol and aldosterone secretion, 200 micrograms of ACTH 1-17 were injected i.m. at 07(00) in two groups of 6 patients each of both sexes. Sampling was done before and after ACTH 1-17 administration at 4-h intervals from 08(00) to 04(00) in order to define the circadian profiles of both cortisol and aldosterone. At the time of study all subjects were kept under the same routine conditions. The i.m. injection of 100 micrograms of ACTH 1-17 was followed by a maximum response of cortisol which coincided with the physiological circadian peak of the hormone (511.7 +/- 122.7 vs 195.5 +/- 92.9 ng/ml; mean +/- 1 SD; p less than 0.001). With this treatment no variations in the normal circadian rhythm were observed. After the injection of 200 micrograms ACTH 1-17, a marked variation in the circadian rhythm of cortisol (peak at 16(00): 390.0 +/- 49.8 ng/ml; mean +/- 1 SD) was observed. Significant variations in the circadian rhythm of aldosterone with respect to the normal profile were observed only after the injection of 200 micrograms ACTH 1-17 (peak at 16(00): 137.5 +/- 50.5 vs 50.8 +/- 36.1 ng/ml; mean +/- 1 SD; p less than 0.01). The hormone increase observed after the injection of 100 micrograms (peak at 08(00): 111.7 +/- 87.5 vs 61.3 +/- 16.5 ng/ml; mean +/- 1 SD) was not statistically significant. Our results indicate that the clinical use of ACTH 1-17 i.m. is not recommended at doses greater than 100 micrograms.(ABSTRACT TRUNCATED AT 250 WORDS)

THE plant hormone abscisic acid (ABA) is thought to be involved in the regulation of transpiration through its effects on stomatal aperture1. Application of synthetic ABA causes stomatal closure in whole plants2, shoots3 and leaf epidermal strips4. During water stress, levels of the hormone increase in plant tissues5, including the leaf epidermis6, and this is usually associated with stomatal closure7. There is evidence that ABA affects the ionic8,9 and metabolic9 status of the stomatal complex and it has been concluded that ABA acts directly on guard cells in effecting stomatal closure8,10,11. There is, however, little information about the distribution of ABA in specific cells of the epidermis or about the sensitivity of the stomatal complex to ABA. We present here evidence that ABA can accumulate in the stomatal complex of Commelina communis L., a species used extensively in studies of stomatal physiology12. The leaves of this plant yield relatively uncontaminated epidermal strips13 and this property has made it possible to calculate the apparent sensitivity of the stomatal complex to ABA. The evidence is based on experiments involving the uptake, distribution and metabolism of exogenous 2-14C-ABA.