This study was aimed at investigating the mechanisms of clinically important overt hyperkalemia in diabetes mellitus with underlying hyporeninemic hypoaldosteronism known as a classic model of the syndrome of hyporeninemic hypoaldosteronism (SHH). Rats (Sprague-Dawley, male) were streptozotocin-treated (60 mg/kg, ip) and used after 60 days. Rats with plasma glucose levels higher than 300 mg/dL (mean +/- SEM, 423 +/- 20 mg/dL, n = 8) were selected as the diabetic group. Age-matched normal rats served as control (mean plasma glucose, 88 +/- 2, mg/dL, n = 8). Serum potassium concentrations and osmolalities as well as serum creatinine levels were significantly higher in the diabetic than in the control group (5.07 +/- 0.09 vs. 4.68 +/- 0.11 mEq/L; 330 +/- 14 vs 290 +/- 3 mOsm/L; 0.40 +/- 0.03 vs 0.31 +/- 0.02 mg/dL, p < 0.05). Plasma renin activity (PRA) in the diabetic group was significantly lower than that in the control group (6.0 +/- 1.0 vs 12.1 +/- 1.1 ng Al/ml/h, p < 0.001). Plasma aldosterone concentration (PAC) was also significantly lower in the former than in the latter (368 +/- 30 vs 761 +/- 57 pg/ml, p < 0.001). Renomegaly, abnormal distal tubular cells with few organelles, and increased lipid droplets with pyknotic nucleus in zona glomerulosa of the adrenal glands were noted in the diabetic group. In conclusion, multifactorial causes including insulinopenia, hyperosmolality, elevated serum creatinine level and hypoaldosteronism with possible contribution of altered distal tubular response to aldosterone may have interacted to develop hyperkalemia in these diabetic rats.
Animals ; Diabetes Mellitus, Experimental/blood/*complications/pathology ; Disease Models, Animal ; Hyperkalemia/*complications ; Hypoaldosteronism/*complications ; Kidney Tubules, Distal/ultrastructure ; Male ; Rats ; Rats, Sprague-Dawley ; Reference Values ; Zona Glomerulosa/ultrastructure

Preadipocyte factor-1 (Pref-1) is expressed in the neuroendocrine organs such as the pituitary gland, the adrenal gland, the pancreas, the testis, etc. Vitamin D3 up-regulated protein 1(VDUP1) gene is known to be a novel member of early response genes as an oxidative stress mediator. The aim of the present study was to investigate whether Pref-1 and VDUP1 is involved in stress response in the adrenal gland following chronic immobilization stress. In situ hybridization for Pref-1 and VDUP1 genes (Pref-1 and VDUP1) was performed in the rat adrenal glands following immobilization stress, 2 hr once daily for 7 days. In situ hybridization analysis revealed that Pref-1 expression was up-regulated in rat adrenal medulla following chronic immobilization stress. However, Pref-1 was down-regulated in the zona glomerulosa of the adrenal cortex following chronic immobilization stress. VDUP1 expression was up-regulated in the zona glomerulosa and the adrenal medulla following chronic immobilization stress. These results show that Pref-1 and VDUP1 may be novel genes responding to chronic immobilization stress in adrenal gland.
Adrenal Cortex ; Adrenal Glands* ; Adrenal Medulla ; Animals ; Cholecalciferol* ; Immobilization* ; In Situ Hybridization ; Oxidative Stress ; Pancreas ; Pituitary Gland ; Rats* ; Testis ; Vitamins* ; Zona Glomerulosa

BACKGROUND: Diabetic patients develop hypoaldosteronism which frequently caused hyperkalemia and metabolic acidosis and diabetic hypoaldosteronism is associated with selective unresponsiveness of aldosterone to angiotensin A-II, but mechanism of defect in A-II stimulated aldosterone response still remain unclear. METHODS: To elucidate the mechanism of defect in A-II stimulated aldosterone response, author evaluated the responses of aldosterone production to A-II, K+, and ACTH in adrenal glomerulosa cells prepared from streptozotocin induced diabetic rats, Inositol triphosphate (IP3) generated by activation of phospholipase C (PLC) and arachidonic acid and lysophospholipids generated by activation of phospholipase A2 (PLA2) were measured in A-II stimulated glomerulosa cells. Radiocalcium efflux and aldosterone response to second messenger of A-II such as PLC, IP3, PLA, AA and protein kinase C activator, 12-o-tetradecanoylphorbol 13 acetate (TPA). RESULTS: 1. Plasma renin activity and aldosterone levels were not different among control rats, untreated and insulin treated diabetic rats. 2. Basal, ACTH and K+ -stimulated aldosterone production were similar in cells from the three groups (p<0.05), but A-II stimulated aldosterone production was significantly decreased in cells from untreated diabetic rats compared with control and insulin treated diabetic rats (p0.05). 4. Aldosterone responses to PLC, IP3, AA and TPA were significantly decreased in glomerulosa cells from diabetic rats compared with control and insulin treated diabetic rats (p<0.05), but aldosterone response to PLA2 was similar among the three groups (p>0.05). 45Ca efflux to PLC, IP3 PLA2 and AA were similar among the three groups (p>0.05). CONCLUSION: These results suggested that decreased A-II-stimulated aldosterone response was present in glomerulosa cells from streptozotocin induced diabetic rats and reversed by insulin treatments. The main defect of altered A-II response of zona glomerulosa might be located in the step after activation of phospholipase and increase of intracellular calcium, and activation of PKC, or distal to that could be one of the causative mechanism.
Acidosis ; Adrenocorticotropic Hormone ; Aldosterone* ; Angiotensin II ; Angiotensins* ; Animals ; Arachidonic Acid ; Calcium* ; Diabetes Mellitus ; Humans ; Hyperkalemia ; Hypoaldosteronism ; Inositol ; Insulin ; Lysophospholipids ; Phospholipases A2 ; Phospholipases* ; Plasma ; Protein Kinase C ; Rats* ; Renin ; Second Messenger Systems ; Streptozocin ; Type C Phospholipases ; Zona Glomerulosa*

Potassium balance in chronic hypokalemia is regulated by ion channels, ion transporters, and various related genes. We isolated general transcription factor IIA (GTF IIA) gene using a DNA chip microassay, a useful method in cloning genes. Northern analysis and in situ hybridization (ISH) were carried out to analyze the expression and localization of GTF IIA mRNA in rat in relation to the amount of potassium in the diet. Isoform-specific 32P-labeled cDNA (Northern analysis) or digoxigenin-labeled cRNA (ISH) probes were used. Northern analysis demonstrated that GTF IIA mRNA was expressed abundantly in testis; modestly in heart, kidney, lung, adrenal gland, liver, and spleen; and weakly in brain, distal colon, duodenum, salivary gland, and stomach. In potassium-restricted animals, GTF IIA expression was decreased in the kidney, adrenal gland, and spleen, but expression was restored to normal levels in L3w. The expression level in the lung was decreased in L3d and L2w, and increased in L1w and L3w. ISH showed that mRNA for the GTF IIA gene was detected in the distal convoluted tubule, S3 segment of the proximal tubule, and cortical collecting duct in the normal group. In potassium-restricted groups, the hybridization signal was detected in the distal convoluted tubule, S3 segment of the proximal tubule, and entire collecting tubule. The signal intensity of the outer and inner medullary collecting ducts was higher in the potassium-restricted group than in the normal group but was decreased in the distal convoluted tubule and S3 segment of the proximal tubule. In the normal group, mRNA of the GTF IIA gene was detected in the zona glomerulosa cells of the adrenal gland, lymphocytes of the marginal zone, germinal center of the spleen, and bronchial epithelium and lymphocytes of the lung. mRNA for the GTF IIA gene was also detected in the cells of the basal portion of the intestinal glands of the distal colon and stomach, and in spermatogonia and spermatocytes of the seminiferous tubule. These results suggest that expression of GTF IIA differs between various tissues and that increased expression of the GTF IIA gene in the outer and inner medullary collecting ducts of the hypokalemic kidney might regulate the ion transporter genes in these segments.
Adrenal Glands ; Animals ; Brain ; Chimera ; Clone Cells ; Cloning, Organism ; Colon ; Diet ; DNA, Complementary ; Duodenum ; Epithelium ; Germinal Center ; Heart ; Hypokalemia ; In Situ Hybridization ; Intestinal Mucosa ; Ion Channels ; Ion Transport ; Kidney ; Liver ; Lung ; Lymphocytes ; Oligonucleotide Array Sequence Analysis ; Potassium ; Prothrombin ; Rats ; RNA, Complementary ; RNA, Messenger ; Salivary Glands ; Seminiferous Tubules ; Spermatocytes ; Spermatogonia ; Spleen ; Stomach ; Transcription Factors ; Zona Glomerulosa