The effect of anti-hypertensive therapy on urinary albumin excretion in Nigerian hypertensives.

The effect of blood pressure control on urinary protein excretion was assessed in 24 benign essential hypertensive subjects (12 males and 12 females). There were 23 controls (11 males and 12 females). Mean ages were 55 and 53 years respectively. Twenty-four hours urine was collected from each subject before and after control of blood pressure, while the controls had only one 24 h urine sample collected. 24 h urinary albumin excretion was assessed using the Bromocresol Green Method. Control of blood pressure in the subjects took an average of eight weeks. Subjects were either given hydroflumethiazide, alpha-methyldopa and/or prazosin as required. Blood pressure was measured in the right arm at each visit and pill counting was used to assess the compliance with therapy. The average urinary albumin excretion was significantly higher in the hypertensive subjects than the normotensive controls (P < 0.05). The average urinary albumin excretion after control of blood pressure was also significantly lower than, before control of blood pressure (P < 0.02). There was no correlation between SBP, DBP, MAP, and 24 h urinary albumin excretion in both subjects and controls. This study has shown that control of blood pressure can reduce or reverse urinary albumin excretion in Nigerian hypertensives.

Photoaugmentation effects demonstrated in vitro.

A number of sulphonamide-derived oral antidiabetics and diuretics were investigated for phototoxic properties, using different sources of light, by means of a photohemolysis test. Photohemolysis was obtained after irradiation with UVA, visible light and solar simulating irradiation. No phototoxic properties were seen when the test samples were exposed to UVB alone. The most prominent hemolysis was induced by solar simulating irradiation. When exposing the the test samples to UVB prior to the subsequently applied UVA, visible light or solar simulating irradiation, a significantly higher hemolysis was detected compared with the previous tests, suggesting photoaugmentation effects in this model.

Do thiazides reduce intestinal oxalate absorption?: a study in vitro using rabbit colon.

1. The purpose of the present study was to examine the effects of various diuretics on intestinal oxalate transport. Transmural oxalate fluxes were measured across isolated, short-circuited tissue segments removed from rabbits and placed in Ussing chambers. 2. The net absorptive flux of oxalate across the distal colon was significantly reduced in the presence of trichlormethiazide at 10(-4) mol/l. In contrast, this diuretic had no effect on oxalate transport in the other intestinal segments examined. Several of the thiazide diuretics tested had some inhibitory effect on colonic oxalate absorption, but at higher concentrations of 10(-3) mol/l or 10(-2) mol/l. 3. We conclude that the previously reported hypooxaluric effects of hydrochlorothiazide and chlorthalidone are most likely not the result of an exclusive or primary effect on intestinal oxalate transport. It is suggested that the reduction in colonic oxalate absorption that was observed with the thiazides probably involves the transport system responsible for oxalate efflux across the basolateral membrane of the colonocyte.

Comparative study of the efficacy and tolerability of hydroflumethiazide versus propranolol in Africans with mild to moderate hypertension.

Sixty patients with Diastolic Blood Pressure (DBP) of 100-110mmHg matched for age, sex and Bp levels were randomly assigned to propranolol 80mg daily or Hydroflumethiazide (HFM) 50mg daily. HFM causes a significant reduction in systolic blood pressure (SBP) and DBP within 4 weeks compared both with baseline and propranolol (SBP 143.7 +/- 12.3 vs 158.1 +/- 10.9mmHg, P < 0.05; DBP 92.0 +/- 4.5 vs 102.4 +/- 5.1mmHg, P < 0.05), (SBP 143.7 +/- 12.2 vs 152 +/- 11.0mmHg P < 0.05; DBP 92.0 +/- 4.5 vs 101.1 +/- 6.1mmHg, P < 0.05), respectively. Propranolol produced no significant difference from the baseline at 4 weeks (SBP 152.0 +/- H.0 vs 154.1 +/- 11.5mmHg NS; DBP 101.1 +/- 6.1 vs 102.2 +/- 5.6mmHg, NS). Reduction in BP by HFM was maintained after 8 and 12 weeks with further reduction but which did not achieve statistical significance. Increased dose of propranolol (160mg daily) after 4 weeks caused significant reduction in BP by 8 week (SBP 146.8 +/- 11.8 vs 152.0 +/- 11.0mmHg, P < 0.05; DBP 95.9 +/- 4.4 vs 101.1 +/- 6.1mmHg P < 0.05), which was maintained upto 12 weeks. The values however remained higher than in the HFM group. More patients in the HFM group achieved target BP (< 140/90), SBP 53.8% vs 29.6% P < 0.05, DBP 69.2% vs 14.8% P < 0.01. Incidence of side effects was similar and will be discussed. Thiazides are superior to B'blockers as initial monotherapy in black hypertensives.

Effect of thiazides on colonic NaCl absorption: role of carbonic anhydrase.

The mechanisms by which the benzothiadiazide class of diuretics inhibit electroneutral NaCl absorption are not fully understood. We studied the mechanisms of thiazide action in perfused loops of distal colon in anesthetized male Sprague-Dawley rats. Hydroflumethiazide (1 mM) reversibly inhibited greater than 40% of Na, Cl, and water absorption. Prior exposure of the colon to the carbonic anhydrase inhibitor methazolamide (0.1 mM) prevented the effects of hydroflumethiazide and metolazone, a thiazide-like drug, on colonic absorption. In Ussing flux chambers, addition of hydroflumethiazide to both the mucosal and serosal bathing solutions (but not to the mucosal solution alone) caused marked decreases in Na and Cl absorption. Such inhibition only occurred at concentrations of hydroflumethiazide (0.1 and 1.0 mM) that inhibited greater than 90% of carbonic anhydrase activity in homogenized colonic mucosa. We conclude that an important mechanism by which thiazides inhibit NaCl absorption in the rat distal colon is by inhibition of mucosal carbonic anhydrase. In tissues containing this enzyme, this mechanism of thiazide effect on ion flux must be considered.

Comparative effects of LN 5330 and diazoxide on insulin release and 86Rb+ permeability in perifused rat islets of Langerhans.

The benzothiadiazine derivative LN 5330 (chloro-7 trifluoromethyl-6 benzothiadiazine-1,2,4-dioxide-1,1) has been shown to inhibit insulin secretion and calcium uptake. The present study was carried out to investigate the effects of LN 5330 on insulin release and 86Rb- efflux from perifused rat pancreatic islets; a comparison was made with the structural analogue diazoxide. In the presence of 8.3 mM glucose, LN 5330 (100 microM) accelerated 86Rb+ efflux while reducing insulin output from the islets. LN 5330 induced a dose-dependent acceleration of 86Rb+ efflux and appeared to be a more potent activator of 86Rb+ efflux than diazoxide. The stimulatory effect of LN 5330 on 86Rb+ efflux persisted in the absence of extracellular calcium. In the absence of glucose, 86Rb+ permeability also increased, LN 5330 being again significantly more efficient than diazoxide at an equimolar concentration. These data indicate that the benzothiadiazine derivative LN 5330 inhibits insulin secretion by increasing the potassium permeability of the plasma membrane. It is suggested that, like diazoxide, this drug could activate the ATP-sensitive K+ channel.

NaCl absorption in the rabbit ileum. Effect of acid-base variables.

In vivo and in vitro studies suggest that acid-base variables regulate ion transport in the rabbit ileum. The relative importance of these variables on active Na+ and Cl- absorption has not been defined. Isolated, stripped ileal segments were studied under short-circuited conditions in the Ussing flux chamber. Unidirectional 22Na and 36Cl fluxes were measured after changes in bathing solution pH, PCO2, and/or [HCO3-]. When pH was decreased from 7.6 to 7.1, net flux of Na+ increased from 0.1 +/- 0.7 to 2.6 +/- 0.7 mu Eq/cm2 per hour and net flux of Cl- increased from -2.0 +/- 0.9 to 1.3 +/- 0.6 mu Eq/cm2 per hour. These changes were rapid in onset, completely reversible, and accounted for by changes in mucosal-to-serosal fluxes of these ions. They were accompanied by small decreases in short-circuit current, but there were no changes in residual flux. These pH effects were not inhibited by the presence of luminal bumetanide (1 mmol/L), furosemide (1 mmol/L), hydroflumethiazide (1 mmol/L), or 4,4'-diisothiocyanostilbene-2,2'-disulfonate (1 mmol/L), or by the carbonic anhydrase inhibitor methazolamide (1 mmol/L). When data from all combinations of acid-base conditions were combined and analyzed by linear regression, pH was the only variable that correlated with mucosal-to-serosal fluxes (r = -0.84) and net flux (r = -0.85) for Na+, mucosal-to-serosal fluxes (r = -0.96) and net flux (r = -0.99) for Cl-, and short-circuit current (r = 0.97). These findings suggest that extracellular pH modulates active Na+ and Cl- absorption in the rabbit ileum.

Effects of single doses of two antihypertensive rauwolfia-diuretic combinations on urinary excretion.

In a double-blind placebo-controlled investigation, 14 healthy adult male volunteers were studied to assess and compare the urinary effects of acute single doses of two antihypertensive formulations containing: hydroflumethiazide 50 mg, Rauwolfia serpentina 50 mg and potassium chloride 625 mg (HFRK) (Rautrax-50; Squibb Laboratories); and clopamide 5 mg, reserpine 0.1 mg and dihydroergocristine 0.5 mg (CRE) (Brinerdin; Sandoz Products). Both significantly increased mean 24-hour urinary outputs of fluid, Cl-, Na+, K+ and Mg2+. CRE increased creatinine and decreased Ca2+ output. After dosing, times to maximal urinary flow of fluid, Cl-, Na+, Ca2+ and creatinine were shortened by HFRK and CRE and those corresponding to K+, Mg2+, phosphate and urate were unaffected. Both formulations thus acted mainly through their diuretic constituents.

Effects of a thiazide diuretic (hydroflumethiazide) and a loop diuretic (bumetanide) on the endocrine pancreas: studies in vitro.

Treatment with thiazide diuretics causes an impairment of the glucose metabolism. To study whether this is due to a direct effect on the endocrine pancreas, the effects of the thiazide hydroflumethiazide on the release of glucagon, insulin, and somatostatin from the isolated perfused pancreas of normal and alloxan diabetic dogs were examined. Hydroflumethiazide at concentrations ranging from 1 to 50 micrograms/mL stimulated the normal secretion of glucagon (P less than 0.001), insulin (P less than 0.001), and somatostatin (P less than 0.001) in a dose-dependent manner. The normal hormone responses evoked by 50 micrograms/mL of the thiazide were, however, modified by the prevailing glucose level: higher insulin (P less than 0.05) and somatostatin (P less than 0.05) and lower glucagon (P less than 0.05) were obtained at the high glucose concentration of 11 mmol/L rather than at the low glucose concentration of 1.3 mmol/L. In alloxan diabetes, insulin secretion was almost extinct and did not respond to hydroflumethiazide, whereas glucagon was dose-dependently stimulated (P less than 0.001). In addition, we looked at the effect of the loop diuretic, bumetanide. The infusion of bumetanide at doses ranging from 0.5 to 3 micrograms/mL did not alter the release of glucagon, insulin, and somatostatin in the presence of 5.5 mmol/L glucose. The results suggest that hydroflumethiazide possesses the ability to directly stimulate A cell secretion in the normal and alloxan diabetic pancreas. Whether this effect is of clinical importance for the diminution in glucose tolerance observed during thiazide therapy remains, however, uncertain.

A new benzothiadiazine derivative, LN 5330: effects on pancreatic hormones.

LN 5330 is a new benzothiadiazine which is a structural analogue of diazoxide. Its effects in vivo were studied on blood glucose levels and insulin, glucagon and somatostatin secretion in normal dogs, and in vitro on glucagon and insulin secretion from the isolated perfused rat pancreas. The results were compared with those obtained with diazoxide at equimolar dose or concentration. In the normal anaesthetized dog having a T-shaped catheter inserted in the pancreaticoduodenal vein, the infusion of LN 5330 (87.8 mumol/kg for 20 min) induced a progressive increase in blood glucose levels, a rapid decrease in insulin and somatostatin output rate, an immediate increase in pancreatic glucagon secretion, and a delayed decrease of arterial blood pressure. The equimolar dose of diazoxide provoked the same effects on blood glucose levels, insulin and somatostatin output, but a marked decrease in glucagon output and in arterial blood pressure. In the isolated rat pancreas perfused with 8.3 mmol/l glucose, the infusion of LN 5330 (440 mumol/l for 30 min) induced a drastic fall in insulin and a rapid and persistent increase in glucagon output. This stimulatory effect on glucagon secretion was not found with diazoxide at equimolar concentration. These findings show that LN 5330 is a substance which is distinct from diazoxide and interesting because of its double action: inhibition of insulin secretion and stimulation of glucagon secretion.

Effect of LN 5330 on insulin release and calcium uptake by isolated rat islets of Langerhans. Comparison with diazoxide.

The effect of a new benzothiadiazine derivative, LN 5330, was studied on insulin release and 45Ca++ uptake by isolated rat islets of Langerhans. LN 5330 (0.1 mmol/l) significantly inhibited both insulin release and calcium uptake of islets incubated in MEM (glucose 8.3 mmol/l). This effect was comparable to that of diazoxide. The withdrawal of LN 5330 from the medium resulted in a significant increase of insulin release and calcium uptake by the islets during a subsequent incubation in MEM (glucose 8.3 mmol/l). In contrast, after withdrawal of diazoxide, insulin release and calcium uptake by the islets were not different from the controls. These results suggest a dual action of LN 5330: an effect, similar to that of diazoxide, responsible for the inhibition of insulin release in the presence of the drug; and an effect, specific to LN 5330, which would induce cellular changes, the consequence of which appears only upon withdrawal of the drug.

Interaction of hydroflumethiazide and 2,4-disulfamyl-5-trifluoromethylaniline with cyclic AMP phosphodiesterase and carbonic anhydrase.

The inhibitory effect of hydroflumethiazide (HFT) and its metabolite, 2,4-disulfamyl-5-trifluoromethylaniline (DTA) on cyclic AMP phosphodiesterase and the binding of HFT and DTA to carbonic anhydrase was studied in vitro. Significant inhibition of rat kidney low-Km cyclic AMP phosphodiesterase was observed with DTA concentration above 2.5 X 10(-4) mol/l and with HFT concentration above 1 X 10(-4) mol/l. 50% inhibition was observed at a DTA concentration of 1 X 10(-3) mol/l. Binding of DTA and HFT to commercially obtained bovine erythrocyte carbonic anhydrase was demonstrated by equilibrium dialysis. Data were consistent with one class of binding sites. The product of n (number of binding sites) and Kass (association constant) was 5 X 10(5) M for DTA and 3.3 X 10(4) M for HFT at 2 degrees. In human blood in vitro at 37 degrees, the equilibrium erythrocyte/plasma concentration ratio was 18 for DTA and 1.6 for HFT. It is concluded that HFT and DTA have approximately the same potency as cyclic AMP phosphodiesterase inhibitors, whereas DTA is more extensively bound by erythrocyte carbonic anhydrase.

Effects of a new benzothiadiazine derivative, LN 5330, on insulin secretion.

The effect of a new benzothiadiazine derivative, LN 5330, was studied on insulin secretion from isolated perfused rat pancreas. LN 5330 (1 mg/l to 125mg/l) induced an inhibition of insulin secretion evoked by glucose 1.5 g/l. In all cases the inhibition recorded during the infusion was followed by an increase in insulin secretion after stopping the infusion. This increase was biphasic with LN 5330 at 1, 3, 5 and 15 mg/l. The insulin increase as well as the insulin decrease were dose-related but the additional amount of insulin released after stopping LN 5330 was higher than the amount of insulin which was not released during the infusion of LN 5330. Diazoxide and somatostatin were infused at concentrations which induced an inhibitory effect similar to that obtained with LN 5330 (15 mg/l). When diazoxide infusion was stopped, only a very transient overshoot appeared and after somatostatin infusion insulin secretion progressively returned to reference value. It is concluded that LN 5330 by inducing inhibition and secondary increase of insulin output might be a valuable tool for studying the mechanisms involved in insulin secretion.

Effect of repeated doses of hydroflumethiazide on renal excretion of electrolytes and uric acid in healthy subjects.

Urinary excretion of electrolytes and uric acid was investigated in six healthy subjects during repeated oral administration of 100 mg hydroflumethiazide (HFT) daily for seven days, and related to urinary thiazide excretion. Mean 24 hr-urinary excretion of sodium and chloride increased 100% (P less than 0.02) after the first HFT-dose, whereas 24 hr-excretion values were at control level after the fourth and seventh doses. Mean 24 hr-urinary excretion of potassium was increased by 31% after the first HFT-dose (P less than 0.05) and by 47% after the fourth dose (P less than 0.05). After HFT was discontinued, mean urinary excretion rates of sodium and chloride dropped to 30% and that of potassium to 70% of control. In the state of fluid deficiency and elevated aldosterone concentration, there was a significant positive correlation between log excretion rate of HFT and excretion rate of sodium (r=0.68, P less than 0.002) calculated from excretion data 0-67, 6-12, and 12-14 hrs after the seventh dose. After the first dose of HFT, sodium excretion was also significantly correlated to log excretion rate of HFT (r=0.86, P less than 0.001) but was probably influenced by other factors as well. Mean serum concentration of uric acid increased significantly, but mean 24 hr-urinary excretion of uric acid was constant during HFT-treatment.

Hypotensive effects of pentobarbital and diuretics on sympathectomized spontaneously hypertensive rats.

The upper abdominal sympathetic chain with the splanchnic nerve was removed bilaterally in spontaneously hypertensive rats(Okamoto-Aoki). After recovery from the operation, the sympathectomized spontaneously hypertensive rats were as hypertensive as intact or sham operated ones. However, anesthesia with pentobarbital or administration of diuretics induced a significantly greater fall of pressure in the sympathectomized hypertensive rats. The hypotensive effect of either drug was insignificant or considerably small, if present at all, in sympathectomized normotensive control rats. It seems that, in intact spontaneously hypertensive rats, the hypotensive effects of pentrobarvital and diuretics are compensated for by a reflex activation of the abdominal sympathetic nerves.

Quinuclidine chemistry. 4. Diuretic properties of cis-3-amino-2-benzhydrylquinuclidine.

A number of 3-amino-2-benzhydrylquinuclidines were tested for diuretic activity in both rats and dogs. The Schiff base formed from 2-benzhydryl-3-quinuclidinone and benzylamine was reduced with NaBH4 to a mixture of isomers, the cis isomer being preponderants. cis-2-Benzhydryl-3-benzylaminoquinuclidine was isolated by chromatography and debenzylat:d to cis-3-amino-2-benzhydrylquinuclidine, the most active compound in this series. The corresponding trans isomer was considerably less active. It was made by reacting the mesylate of cis-2-benzhydr-l-3-quinuclidinol with Nan3 to form trans-3-azido-2-benzhydrylquinuclidine which was reduced with LiAlH4. In dose-response studies (sodium excretion as a function of dose) in rats the maximal or ceiling effect of cis-3-amino-2-benzhydrylquinuclidine was considerably greater than that of hydroflumethiazide but less than that of furosemide. An unusual biphasic dose-response was seen in dogs with cis-3-amino-2-bezhydrylquinuclidine, centering around 10 mg/kg.