REDUCED GROWTH OF THE ADRENAL ZONA GLOMERULOSA AFTER NEONATAL TREATMENT OF FEMALE RATS WITH SRIH-14 .

array of biological actions, including the inhibition of hormone secretion, modulation of neural transmission and regulation of cell growth (F l o r i o et al., 1999). At the periphery, SRIH inhibits the secretion of several non-pituitary hormones such as insulin, glucagon, gastrin, secretin and aldosterone (R e i c h l i n , 1983; M i l o š e v i ć , 1999). Within the nervous system, SRIH acts as a neuromodulator, affecting neuroendocrine, motor, and cognitive functions (R e i c h l i n , 1983; E p e l b a u m et al., 1994). Because of its ability to inhibit secretory functions of various organs, its therapeutic value in clinical conditions is recognized and used.

Somatostatin is a circulating peptide hormone that displays an array of biological actions, including the inhibition of hormone secretion, modulation of neural transmission and regulation of cell growth (Florio et al., 1999).At the periphery, SRIH inhibits the secretion of several non-pituitary hormones such as insulin, glucagon, gastrin, secretin and aldosterone (Reichlin, 1983;Milošević, 1999).Within the nervous system, SRIH acts as a neuromodulator, affecting neuroendocrine, motor, and cognitive functions (Reichlin, 1983;Epelbaum et al., 1994).Because of its ability to inhibit secretory functions of various organs, its therapeutic value in clinical conditions is recognized and used.
In view of the above, the purpose of this study was to examine the effects of administration of SRIH-14 on morphological and stereological features of adrenal zona glomerulosa (ZG) cells in neonatal female rats.Time-mated pregnant Wistar rats were housed individually and maintained in a controlled environment (12 h light: 12 h dark; 22 ± 2°C), with food (product of Veterinarski zavod Subotica, Subotica, Serbia and Montenegro) and water freely available.Female pups of the first group were injected s.c.twice a day (8 am and 8 pm) with 20 µg of SRIH-14 (S9129, Sigma, St. Louis, Mo., USA) per 100g b.w. for five consecutive days (from the 3 rd to 7 th day of life).Those of the second group served as the control, and receivedphysiological saline.All animals were sacrificed by decapitation under deep anesthesia 12 h after the last treatment.Experimental protocols were ones approved by the Local Animal Care Committee and conformed to the recommendations given in "Guide for the Care and Use of Laboratory Animals" (1996, National Academy Press, Washington, D. C.).
The left adrenal gland was excised, fixed in Bouin's solution, embedded in paraffin, and serially cut into sections 5 µm thick.The sections were stained with hematoxylin-eosin and stereologically analyzed using the M 42 multipurpose test system inserted into the ocular of a Zeiss light microscope.The volume densities of nuclei and cytoplasm of parenchymal cells were estimated ata total magnification of x 1000.For each adrenal gland, a single paraffin section containing medulla was chosen and 30 test areas of the ZG were stereologically analyzed.On the basis of earlier karyometric studies (Malendowicz, 1974), the β shape coefficient was assumed to be 1.500 for ZG cells.It relates N v (number of cells counted per unit of volume) to N a (number of cells counted per mm 2 ) and V v (volume density) and depends on the axial ratio of estimated nuclei.The number of adrenocortical cell nuclei per mm 3 was calculated according to the method of Weibel(1979).
The ZG cells werearranged in closely packed ovoid clusters.The cells were relatively small, columnar or pyramidal in shape.Their nuclei were round or oval, with an evidenced nucleolus.In these cells lipid droplets were observed.The shape of ZG cells in animals neonatally treated with SRIH-14 was not significantly changed, but the cytoplasm of these cellswas darkly stained in comparisonto the controls (Fig. 1A, B).Absolute and relative volumes of the ZG were significantly (p <

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0.05) reduced by 36% and 20%, respectively, in comparison with control values (Table 1).The volumes of ZG cells and their nuclei were significantly (p < 0.05) reduced by 7% and 15%, respectively, in comparison with control values.
Our results strongly suggest that neonatal treatment of female rats with SRIH-14 suppresses growth of the adrenal ZG and its cells.These results are in accordance with earlier observations of Mazzocchi et al. (1985) and Robba et al. (1986), who showed that SRIH-14 has a direct inhibitory effect on growth and functional capacity of the adrenal ZG.Pawlikowski et al. (1990) also reported a reduced basal proliferation rate of these cells,probably owing to blocked basal trophic action of angiotensin-II (Aguilera et al., 1981).Rebuffat et al. (1994) found that SRIH-induced atrophy of the ZG and its parenchymal cells affected the mitochondrial and smooth endoplasmic reticulum cell compartments, while Kong et al. (1994) showed that the rat adrenal gland manifested a high level of SRIH-receptor mRNA, implying direct somatostatine influence on the adrenal gland.However, earlier studies of Milošević et al. (1996Milošević et al. ( , 1997) ) and Näsman et al. (1995) showed that intracerebroventricular application of SRIH reduced size of the ZG and the volume of its cells by influencing the regulatory hypothalamic-pituitary axis.
Based on these results, it can be concluded that neonatal application of SRIH-14 inhibits growth of the adrenal ZG and its cells in female rats.