Angiotensin-I-converting enzyme activity in idiopathic respiratory distress syndrome of the newborn infant and in experimental alveolar hypoxia in mice

Serum angiotensin-I-converting enzyme activity was found to be elevated in infants with idiopathic respiratory distress syndrome when compared with healthy premature infants, normal infants, and acutely ill full-term infants. Serum and lung CE activity has been found to be elevated in mice exposed to hypobaric alveolar hypoxia which also stimulated renal renin production. These findings suggest that alveolar hypoxia stimulates the renin-angiotensin-aldosterone system and this system may be involved in the response to the stress of IRDS.

Hypertension and narrowing of the renal arteries in infancy

The clinical histories of two infants who had severe hypertension and stenoses of the renal arteries are reported. In both children blood pressure fell significantly after surgical correction of renal ischemia. However, both infants had persistent mild hypertension for several months after surgical treatment. Similar results were found in other infants with renovascular hypertension, reported previously (11 cases). The mortality rate in this total group of 13 infants reviewed was high if renal ischemia was not corrected surgically (4/4). The reason why some infants have persistent hypertension after apparently adequate surgical relief of renal ischemia is not known.

Irreversibility of methylandrostenediol-induced hypertension in the rat after suspension of the androgen treatment

Administration of 10 mg of methylandrostenediol for 10 weeks to uninephrectomized, salt drinking, female Sprague Dawley rats caused severe hypertension with extensive renal and cardiovascular damage. The hypertension was accompanied by increased consumption of sodium, high sodium levels in peripheral plasma, decreased weight of the pituitary, thymus, adrenals and ovaries and decreased content of renal renin. Methylandrostenediol treatment also produced impairment of normal adrenal steroidogenesis, reflected in elevated production in vitro of 11-deoxycorticosterone during incubation of adrenal gland homogenates with (14)C-progesterone. Such increased production of deoxycorticosterone is probably responsible for the development of the hypertensive disease. If the methylandrostenediol-treated animals were kept alive for 12 additional weeks after suspension of the treatment with the androgen, the hypertension, as well as the high sodium consumption, high plasma sodium concentrations and low levels of renal renin, persisted to the end of the experiment. The cardiovascular and renal lesions in these animals, killed 12 weeks after suspension of the androgen administration, were similar to those seen in the rats receiving methylandrostenediol but killed at the tenth week of the treatment. Suspension of methylandrostenediol administration, however, resulted in a return to normal weight of the pituitary, thymus, adrenals and ovaries within 12 weeks. Normal amounts of deoxycorticosterone were formed in vitro by the adrenal glands of these rats and the return to normal structure was also confirmed by a electron microscopic study. Thus, contrary to a previous experiment where methylandrostenediol was given for a shorter period of time and the hypertension was reversible, it was shown in this study that metacorticoid hypertension is induced by methylandrostenediol administration, as it is with treatment with deoxycorticosterone. Since adrenal steroidogenesis returned to normal, some other mechanisms must be involved in maintaining the hypertension. It is very likely that these factors are consequent to the extensive and irreversible renal and cardiovascular damage.

Recovery of adrenal ultrastructure after cessation of androgen treatment

Female, uninephrectomized rats injected with methylandrostenediol became hypertensive by 4 weeks of treatment. After cessation of treatment, blood pressure continued to rise during the first week but gradually decreased below the borderline of hypertension by 5 weeks. After methylandrostenediol treatment for 4 weeks and after 1 week of recovery, adrenocortical fine structure exhibited a number of abnormalities including reduced numbers of mitochondrial cristae, hypertrophic smooth endoplasmic reticulum, microfilaments and large lipid vacuoles within zona reticularis cells. During an intermediate period of recovery (2 weeks), mitochondrial cristae increased in number, although animals remained hypertensive. After 2 weeks, all of the ultrastructural abnormalities seen at early and intermediate periods of recovery were fully reversed, concomitant with a return of systolic blood pressure to below hypertensive levels.