Adrenal and vascular tyrosine hydroxylase activity in Goldblatt hypertension

Wnt/β-catenin signaling in the adrenal glands of rats in various types of experimental hypertension

Wnt/β-catenin signaling plays a key role in maintaining homeostasis, which is disturbed in hypertension. Taking into account the lack of literature describing changes in the Wnt/β-catenin pathway in the adrenal glands under conditions of elevated arterial pressure, here we compare the expression of WNT4, WNT10A, β-catenin, and GSK-3β in the adrenal glands of hypertensive rats of various etiologies. The studies were carried out on the adrenal glands of rats with spontaneous hypertension (SHR), renalvascular (2K1C), and deoxycorticosterone acetate (DOCA)-salt. Immunohistochemical and PCR methods were used to identify the molecular components of the canonical signaling pathway and to evaluate gene expression. Immunoreactivity and expression of WNT4, WNT10A, β-catenin, and GSK-3β in adrenals of SHR was decreased, compared to control rats. In adrenals of 2K1C rats, intensity of immunohistochemical reaction and expression of WNT4 and β-catenin was lower, while immunoreactivity and expression of WNT10A and GSK-3β were higher, compared to normotensive animals. Significantly stronger immunoreaction and expression of WNT4, β-catenin and GSK-3β but weaker immunoreactivity and expression of WNT10A were noted in adrenals in DOCA-salt rats, compared to control rats. In conclusion, our data provide new molecular information indicating that the canonical WNT pathway is disrupted in the adrenal glands of hypertensive rats. They show that the dysregulation of the WNT pathway depends on the etiology of hypertension.

Effect of dietary NaCl on tyrosine hydroxylase in the superior cervical ganglia of Dahl rats

To investigate the involvement of peripheral catecholamines in the development of Dahl-Iwai salt-sensitive (DIS/Eis) hypertension, we performed immunohistochemical staining of tyrosine hydroxylase (TH) in the superior cervical ganglia (SCG) of DIS/Eis rats and Dahl-Iwai salt-resistant (DIR/Eis) rats, and in situ hybridization histochemistry for demonstration of TH mRNA localization in the SCG of these rats. DIS/Eis and DIR/Eis rats were fed on a high (8%) salt diet or on a low (0.3%) salt diet for 4 weeks. Nerve cells in the SCG of DIS/Eis high salt rats exhibited more intense TH-immunoreactivity (P < 0.01) and hybridization signals (P < 0.01) than those of the other experimental groups. These findings suggest that activation of peripheral sympathetic nerves may account for hypertension in DIS/Eis rats on a high salt diet.

Norepinephrine turnover in the heart and blood vessels of Goldblatt hypertensive rats

The norepinephrine (NE) content, the uptake of [3H]NE, the turnover time, the turnover and the synthesis rate of the neurotransmitter in the heart and blood vessels were studied in the chronic phase of two kidney and one kidney Goldblatt renovascular hypertension, in the rat. Intact and sham operated animals were used as controls. Fifty percent of the rats subjected to renal clipping developed hypertension. This fact allowed us to compare changes in clip operated hypertensive and normotensive animals. The weight of the hearts and blood vessels was significantly increased in clip operated rats. Changes were greater in hypertensive animals. NE concentration and total content in the heart and in the artery wall were significantly decreased in the clipped rats. [3H]NE uptake was significantly diminished in the heart of experimental animals; in the artery wall, uptake was much lower than in the heart but no differences were observed between clip operated and sham animals. The turnover of NE was not different among control and clip operated rats either in the heart or in the blood vessels. Synthesis rate was lower in hypertensive animals than in their respective controls, explaining the lower concentration of the amine in cardiovascular tissues. The present data do not suggest that an increased turnover of NE in the cardiovascular sympathetic nerve endings is involved in the maintenance of high blood pressure in both types of Goldblatt renovascular hypertension.

Catecholamine secretory vesicles. Augmented chromogranins and amines in secondary hypertension

Chromogranins A and B are major soluble proteins in chromaffin granules. Their adrenomedullary content is increased in the spontaneously (genetic) hypertensive rat. Is augmented catecholamine vesicular storage of the chromogranins a specific feature of genetic hypertension? To explore this question, we measured chromogranin A immunoreactivity, using a novel, synthetic peptide radioimmunoassay, in rat adrenal medullas 4-6 weeks after induction of the two-kidney, one clip Goldblatt model of renovascular hypertension and in unmanipulated control animals. We also measured messenger RNAs of chromogranins A and B and dopamine beta-hydroxylase by Northern blot. Immunoreactive adrenal chromogranin A was 3.3-fold higher (p < 0.01) in clipped rat adrenals. Adrenal catecholamine concentrations and phenylethanolamine-N-methyltransferase activity were also higher in clipped rats. Adrenal dopamine beta-hydroxylase activity (both membrane-bound and soluble forms) and corticosterone (glucocorticoid) concentration did not significantly differ between the groups. Adrenal medullary chromogranin A messenger RNA levels in clipped rats were 3.2-fold higher (p = 0.029) than those in the control group, and chromogranin B messenger RNA levels were 4.6-fold higher (p = 0.05). Dopamine beta-hydroxylase messenger RNA levels were 2.9-fold higher (p = 0.038). Thus, augmented synthesis and storage of adrenomedullary chromogranins A and B, catecholamines, and their biosynthetic enzymes appear to be characteristic of both acquired and genetic hypertension.