Somatostatin analog (SMS 201-995) inhibits the basal and angiotensin II-stimulated 3H-thymidine uptake by rat adrenal glands

Angiotensin II and Angiotensin Receptors 1 and 2-Multifunctional System in Cells Biology, What Do We Know?

For years, the renin-angiotensin system (RAS) has been perceived as a system whose role is to primarily modulate the functioning of the cardiovascular system. Years of research into the role of RAS have provided the necessary data to confirm that the role of RAS is very complex and not limited to the cardiovascular system. The presence of individual elements of the renin-angiotensin (RA) system allows to control many processes, ranging from the memorization to pro-cancer processes. Maintaining the proportions between the individual axes of the RA system allows for achieving a balance, often called homeostasis. Thus, any disturbance in the expression or activity of individual RAS elements leads to pathophysiological processes.

Adrenal cortex in peripubertal and adult female rats after neonatal treatment with SRIH-14

Neonatal female rats (3-7 days old) were injected subcutaneously twice daily with 20 ?g of SRIH-14/100g b.w. for five consecutive days. The animals were sacrificed in the peripubertal (38 days old) or adult (80 days old) periods of life. Control rats were treated in the same way with identical volumes of saline. SRIH-14 led to significant reduction (p<0.05) of the absolute and relative volumes of the ZG in peripubertal animals, by 11 and 22%, respectively in comparison with the controls. The total number and volume of ZG cells and their nuclei were also significantly decreased (p<0.05) in peripubertal SRIH-14-treated rats as compared to the controls. There were no significant (p>0.05) changes in the morphometric parameters of adult adrenal cortex after SRIH-14 treatment compared with control females. It can be concluded that subcutaneously applied SRIH-14 in the neonatal period inhibits growth of adrenal ZG cells in female rats only up to the peripubertal stage, while the adrenal gland cortex recovers before mature adulthood is reached.

Somatostatin does not affect multiplication of granule cells in the rat cerebellum

Somatostatin receptor are transiently expressed by immature granule cells of rat cerebellum. The effects of somatostatin and octreotide on cell proliferation were studied in cultured cerebellar explants from 10-day-old rats. Cell multiplication was measured using [3H]thymidine incorporation and flow cytometric analysis of cell cycle parameters. [3H]Thymidine incorporation occurred exclusively in neuroblasts of the external granule cell layer in the presence of insulin (1 microM). The labeling index, the length of the S phase, and the potential doubling time were similar in vivo and in explants. Octreotide (10(-12) to 10(-6)M) had no effect on [3H]thymidine incorporation in cerebellar explants. In addition, somatostatin and octreotide did not modify the proportion of cells in the S, G0-G1, and G2-M phases. The present results demonstrate that somatostatin does not affect cell multiplication in neurons of the external granule cell layer.

Proliferogenic effect of neurotensin (NT) and neuromedin-N (NMN) on the rat adrenal cortex: evidence that angiotensin-II mediates the effect of NMN, but not of NT

NT and NMN, two biologically active peptides acting via the same specific receptor, are both able to stimulate in vivo the proliferative activity of rat adrenocortical cells. The present study aimed to investigate whether the mechanism underlying this effect of NT and NMN may involve an enhanced production of angiotensin-II (ANG-II), a potent adrenocortical proliferogenic factor. Metaphases per adrenal section were counted 120 min after vincristine injection. A bolus administration of ANG-II resulted in a marked increase in the number of metaphase-arrested cells 12, 24 and 48 h after the beginning of the experiment; the concomitant administration of saralasin (SAR), a competitive antagonist of ANG-II, completely blocked the proliferogenic effect of ANG-II. NT-evoked rise in the number of metaphases occurred 48 h after administration and was not influenced by the simultaneous SAR injection. On the contrary, NMN injection induced a burst of adrenocortical cell proliferation within 12 h, and this effect was prevented by SAR. These data suggest that ANG-II mediates the proliferogenic effect of NMN, but not that of NT.

Evidence that endogenous somatostatin (SRIF) exerts an inhibitory control on the function and growth of rat adrenal zona glomerulosa. The possible involvement of zona medullaris as a source of endogenous SRIF

The effect of SRIF and its antagonist cyclo(7-aminoheptanonyl-Phe-D-Trp-Lys-Thr magnitude of Bzl)(SRIF-A) were studied in sham-operated and bilaterally adrenalectomized rats bearing ACTH- and angiotensin II (ANG-II)-responsive adrenocortical autotransplants. SRIF-A (10(-5) M) completely annulled SRIF (10(-6) M)-induced inhibition of ANG-II (10(-8) M)-evoked rise in aldosterone (ALDO) secretion by both dispersed zona glomerulosa (ZG) cells and autotransplant slices. A 7-day intraperitoneal infusion with SRIF (0.3 nmol.kg-1.min-1) significantly lowered plasma ALDO concentration (PAC) in both groups of animals, without affecting plasma renin activity and the plasma levels of ACTH and corticosterone. This treatment caused a marked atrophy of adrenal ZG and its parenchymal cells (without inducing any significant change in the zona fasciculata morphology), as well as of ZG-like cells of autotransplants. Isolated ZG cells and autotransplant slices from SRIF-infused rats evidenced a notable decrease in both their basal and maximally ACTH- or ANG-II-stimulated ALDO production. The simultaneous infusion of rats with SRIF-A (3 nmol.kg-1.min-1) completely reversed all these effects of SRIF. The prolonged infusion with SRIF-A alone caused, in sham-operated rats, a marked increase in PAC and a significant hypertrophy of ZG and ZG cells; basal and maximally-stimulated ALDO secretion of dispersed ZG cells was also notably raised. Conversely, SRIF-A infusion did not evoke any appreciable effect in autotransplanted rats. These findings suggest that endogenous SRIF is specifically involved in the negative control of the secretion and growth of the rat adrenal ZG. Since regenerated adrenocortical autotransplants, which are responsive to SRIF but not to SRIF-A infusion, are completely deprived of chromaffin cells, the hypothesis is advanced that adrenal zona medullaris may be the source of endogenous SRIF regulating ZG function.