Down-regulation of soluble guanylyl cyclase in the inner medulla of DOCA-salt hypertensive rats.
Our laboratory has recently shown increased renal expression of NO synthase 3 (NOS3) in the deoxycorticosterone acetate (DOCA)-salt rat model of hypertension suggesting an up-regulation of the nitric oxide (NO)-cyclic guanosine-3',5'-monophosphate (cGMP) pathway. The present study was designed to determine changes in renal soluble guanylyl cyclase (sGC) activity and expression in the DOCA-salt hypertensive rat. Rats were uninephrectomized and subcutaneously implanted with either a placebo or DOCA-salt pellet. Placebo-treated animals were given tap water ad libitum, while DOCA-treated animals received 0.9% NaCl solution to drink. Each week, rats were placed in metabolic cages for 24 h collection of urine samples. Urine samples were measured for cGMP concentrations using a scintillation proximity method. After 3 weeks, kidneys were removed and dissected into cortex, outer medulla, and inner medulla. Each region of the kidney was further separated into detergent-soluble and detergent-insoluble fractions. DOCA-treated rats exhibited significant increases in urinary cGMP excretion (27.0+/-1.4 fmol/mg creatinine) after 1 week compared to placebo control animals (8.7+/-0.6 fmol/mg creatinine). This was followed by a significant decrease by the second week of treatment (5.4+/-1.0 and 11.4+/-0.6 fmol/mg creatinine in DOCA-salt and placebo, respectively) and a return to placebo values by the third week of treatment (16.2+/-3.1 and 12.9+/-1.0 fmol/mg creatinine in DOCA-salt and placebo, respectively). Western blot analysis of inner medullary detergent-soluble fraction indicated a decrease in the expression of the beta(1)-subunit of sGC in the third week of DOCA-salt-treated animals as compared to placebo controls (n=5 animals per group) while expression of the alpha(1)-subunit was unchanged. Western blot analysis of cortex and outer medullary preparations comparing placebo controls and DOCA-salt-treated animals revealed no difference in alpha(1)- or beta(1)-sGC protein expression. These data suggest an uncoupling of NOS/NO and sGC/cGMP pathways in the renal inner medulla of the DOCA-salt hypertensive rat.
D000818:Animals; D015153:Blotting, Western; D003404:Creatinine / Q000378:metabolism; D006152:Cyclic GMP / Q000378:metabolism / Q000652:urine; D003900:Desoxycorticosterone; D004195:Disease Models, Animal; D004231:Diuresis; D015536:Down-Regulation; D006162:Guanylate Cyclase; D006973:Hypertension / Q000139:chemically induced / Q000378:metabolism*; D007679:Kidney Medulla / Q000378:metabolism*; D008297:Male; D021122:Protein Subunits / Q000096:biosynthesis; D051381:Rats; D017207:Rats, Sprague-Dawley; D018160:Receptors, Cytoplasmic and Nuclear / Q000096:biosynthesis*; D017673:Sodium Chloride, Dietary; D000071756:Soluble Guanylyl Cyclase; D013997:Time Factors
D021122:Protein Subunits; D018160:Receptors, Cytoplasmic and Nuclear; D017673:Sodium Chloride, Dietary; D003900:Desoxycorticosterone; D003404:Creatinine; D006162:Guanylate Cyclase; D000071756:Soluble Guanylyl Cyclase; D006152:Cyclic GMP