Monotherapy in the treatment of hypertension

Approximately 600 people with mild to moderate hypertension were treated with a regimen that started with monotherapy. Reduction in sodium intake achieved adequate blood pressure control in 38 percent, higher than that achieved without therapy (17 percent). Chlorothiazide and propranolol gave satisfactory blood pressure control in 43 and 56 percent of patients, respectively, as sole therapy. When initial blood pressure was greater than 110 mm Hg, satisfactory control was achieved in fewer patients (sodium restriction, 13 percent; chlorothiazide, 30 percent, propranolol 38 percent); in this group, therapy with reduction of sodium intake alone is rarely effective. All measures were about equally successful in treating isolated systolic hypertension. The group given thiazide diuretics alone had an increased number of deaths from myocardial infarcts compared with other groups. This was not seen if a beta-blocking drug or a centrally-acting drug was used in conjunction with the thiazide diuretic. Monotherapy can successfully reduce blood pressure in most patients with mild hypertension. No regimen can be stated to be unequivocally superior to another.

The use of centrally acting antihypertensive drugs in patients with renal disease

Clonidine was given to patients with essential hypertension, renovascular hypertension, and hypertension with parenchymal renal disease. The drug was effective in all groups but was more effective in patients with high plasma renin concentration. Renal function did not deteriorate when the drug was used, and there was an increase in renal blood flow and a small increase in glomerular filtration rate in those with renovascular or essential hypertension. These changes may have been due to falls in plasma renin. Clonidine can be used in patients with renal disease and does not cause worsening of renal function.

The effect of sodium intake on the blood pressure related to age and sex

Two hundred and one volunteers with no known hypertension and 60 patients with untreated hypertension were entered into a study that compared the effect of two levels of sodium intake on blood pressure. One hundred and fifty-four volunteers and 46 hypertensive patients reached compliance goals, with a urinary sodium excretion on the high sodium diet twice that on the reduced sodium intake. The blood pressure on the high sodium diet was 4.5 +/- 0.5 mmHg (n = 154 p less than 0.001) higher than on the reduced sodium diet in normotensive individuals and was increased by 8.4 +/- 1.5 mmHg (n = 46 p less than 0.001) in hypertensive individuals. In the volunteer group the major rise in blood pressure occurred in people over the age of 50. In the hypertensive patients the alteration in blood pressure was not age dependent. In the younger age groups some individuals had an increase in blood pressure when on the high sodium intake which was outside the spontaneous variations in blood pressure of a control group. This implied that a number of young normotensive individuals were susceptible to this alteration in sodium intake. Changes in sodium intake alter blood pressure in hypertensive people, in normotensive people over 50 and in a small number of younger normotensive people. Overall reduction of sodium intake from 200 - 70 mmol/day would reduce the blood pressure level of the population and would reduce the number of people who have a blood pressure that requires drug therapy.

The permeability of collecting ducts to 22Na+ and 36Cl- in rat isolated papillae

1. The diffusional permeability of collecting ducts to 22Na+ and 36Cl- was measured in rat papillae in vitro. 2. The permeability of the collecting duct to 36Cl- was 0.72 (s.e.m. = 0.01; n = 356) microns/sec which was significantly higher than the value of 0.51 (s.e.m. = 0.01; n = 356) microns/sec measured for 22Na+. 3. Collecting ducts in papillae taken from rats on a high sodium intake had a 22Na+ permeability of 0.63 (s.e.m. = 0.04; n = 53) microns/sec which was significantly higher than the value on a normal salt intake (0.50, s.e.m. = 0.04; n = 46 microns/sec). 4. When papillae from normal rats were studied in plasma taken from salt loaded rats, the 22Na+ permeability of 0.59 (s.e.m. = 0.04; n = 18) microns/sec was significantly higher than when incubated in plasma from normal rats (0.44, s.e.m. = 0.05; n = 12) microns/sec. 5. An extract of urine with natriuretic activity had no effect on 22Na+ permeability when tested in this system. 6. Adrenalectomy, PGE2, indomethacin and antidiuretic hormone had no significant effect on 22Na+ and 36Cl- permeability. 7. A substance exists in plasma from salt loaded animals that increases the permeability of collecting ducts to sodium. This effect could explain the component of the natriuresis that follows saline infusion which is independent of changes in glomerular filtration rate, aldosterone, or proximal tubule reabsorption.

Changes in "active" and "inactive" renin in the juxtaglomerular apparatuses of rat nephrons and plasma induced by different salt intake

The juxtaglomerular apparatuses (JGA) of deep and superficial nephrons were isolated by microbiopsy or by microdissection. Inactive renin content was determined by acidification of JGA or plasma to pH 3.0. In rats with low salt intake the renin content of superficial JGA was 13.4 +/- 3.0 ng AI/JGA/h before and 20.4 +/- 3.4 ng AI/JGA/h (n = 9), P less than 0.05) after acidification. The corresponding values for deep JGA were 9.1 +/- 1.2 ng AI/JGA/h and 12.7 +/- 2.7 ng AI/JGA/h (n = 9, P less than 0.01). The plasma renin concentration was 54.1 +/- 15.0 ng AI/ml/h before and 56.0 +/- 10.6 ng AI/JGA/h (n = 7, N.S.) after acidification. In rats with a normal salt intake the superficial renin JGA renin content was 11.6 +/- 2.3 ng AI/JGA/h before and 11.0 +/- 2.7 ng AI/JGA/h (n = 9, N.S.) after acidification. The renin content of deep JGA was 4.6 +/- 0.6 ng AI/JGA/h before and 8.6 +/- 3.1 ng AI/JGA/h (n = 9, P less than 0.005) after acidification. Plasma renin concentration was 34.5 +/- 4.7 ng AI/ml/h and did not change after acidification. In rats with a high salt intake superficial JGA content was 6.8 +/- 1.7 ng AI/JGA/h before and 8.4 +/- 2.1 ng AI/JGA/h (n = 9, N.S.) after acidification. The corresponding values for deep JGA were 5.7 +/- 1.6 ng AI/JGA/h and 6.9 +/- 1.6 ng AI/JGA/h (n = 9, N.S.) respectively. Plasma renin concentration was 13.1 +/- 1.1 ng AI/ml/h and this to 21.8 +/- 2.9 ng AI/ml/h (n = 8, P less than 0.01) after acidification. These results suggest that although the synthesis of active and inactive renin is linked, the secretion of the two forms may be independent.

The effect of sodium intake on blood pressure related to the age of the patients

1. Sodium intake was varied in 182 normotensive volunteers. 2. systolic blood pressure rose by 3.3 (s.e.m. = 0.9) mmHg supine, 2.8 (s.e.m. = 0.7) mmHg erect. 3. Diastolic blood pressure rose by 2.7 (s.e.m. = 0.8) mmHg supine, 2.6 (s.e.m. = 0.8) mmHg erect. 4. In people over 50 y the rise was 12.4/8.1 mmHg (supine) and 9.1/7.1 mmHg (erect). 5. Blood pressure rose as sodium intake increased. Most of the rise was in the older patients but about 25% of younger patients were sensitive to sodium.

Formation and activation of renin in vivo

Active and acid activated renin was measured in glomeruli of rats obtained by microbiopsy and in rat plasma. Sodium depletion increased total and active renin in the juxtaglomerular apparatus and approximately one third of the renin was in an inactive form in sodium depletion. Sodium loading decreased active and total renin and there was no inactive renin present. In plasma changes in a similar direction occurred for active and total renin but in sodium depletion there was no inactive renin present while with sodium loading approximately 40% was in the inactive form. Haemorrhage caused a release of active renin in both sodium states and did not alter the renin content of the J.G.A. Increased delivery of sodium chloride to the macula densa increased the active renin content of J.G.A. but did not alter the total renin content. These results are compatible with two different roles of the renin angiotensin system. One being concerned with intrarenal regulation of glomerular filtration and renal blood flow and the other with maintenance of vascular tone. The conversion of inactive renin to active renin being of particular importance in the regulation of G.F.R.

The effect of prostaglandin E2 and ADH on diffusional water permeability in collecting duct of an isolated rat papilla

The effect of prostaglandin on diffusional water permeability has been studied in collecting ducts in an isolated rat papilla. PGE2 increased water permeability. The effect was significant at a concentration of 10(-8) mol 1(-1) and was maximal with a concentration of 10(-6) mol 1(-1). The maximal increment of 0.94 +/- 0.10 (SEM) micron s-1 was approximately half that produced by maximal stimulation with antidiuretic hormone (2.18 +/- 0.12 micron s-1). A concentration of 10(-8) mol 1(-1) produced an increase in basal water permeability and 24 mu unit ml-1 ADH, which without PGE2 present gave a similar increase, had no incremental effect. ADH 100 mu unit ml-1 increased permeability to a value similar to that observed in the absence of PGE2. Thus PGE2 and ADH both increase water permeability but the increments are not additive. Indomethacin in a concentration that inhibited prostaglandin production altered the response of the collecting duct to ADH. The dose response curve was shifted to the left and the maximal increase in water permeability and the lowest dose at which a response occurred took place at concentrations less than 1/2 those required in its absence. Prostaglandins influence the action of ADH and it is likely that in life they regulate and modulate the change in water permeability induced by anti-diuretic hormone.

A method for the noninvasive evaluation of cardiovascular dynamics using a digital radiographic device

The authors describe a technique for visualizing and quantitating blood flow and cardiac dynamics following the intravenous administration of contrast material (less than 1 ml/kg). This method uses a digital radiographic device while motion by the patient or test subject is stopped. Preliminary flow studies of the carotid arteries and heart of a dog are presented. This technique has the potential to quantitate physiological parameters such as relative blood flow through pairs of arteries, cardiac output, regional ejection fraction, and heart-wall movement and thickening.

Sodium intake, blood pressure and red cell sodium efflux

A series of studies have been undertaken correlating sodium intake, blood pressure and red cell 22Na efflux. The results for male and female patients differ. In male patients with elevated blood pressure, increased sodium intake caused a rise in blood pressure and a fall in red cell 22Na efflux rate. In female patients the results were variable and while certain females followed the above pattern, others had the converse response. Evidence is presented that the change in red cell 22Na efflux is due to a factor in plasma that inhibits the ouabain sensitive component of sodium efflux. This increases after acute and chronic sodium loading and may be similar to natriuretic factor described previously. It is postulated that increased sodium intake causes hypertension by producing a humoral factor that inhibits sodium transport out of cells and that this alters the calcium content of muscle cells and increases their contractility and thus produces hypertension.

Active and inactive renin in individual juxtaglomerular apparatuses

1. Renin was measured in individual juxtaglomerular apparatuses before and after acidification in vitro. 2. Active renin increased with delivery of extra sodium by microperfusion to the macula densa and this increase was similar to that achieved with acidification. 3. In rats pretreated with an inhibitor of protein synthesis active renin increased when extra sodium was delivered to the macula densa. 4. Salt intake changed the amount of renin present in the juxtaglomerular apparatus. In rats on a high salt intake the total renin was low and was all in an active form.

Long-term experiences with labetalol

Labetalol has been used in 83 patients with severe hypertension resistant to a wide number of drugs. Adequate blood pressure control was achieved in 50 patients. Seven patients with a response in blood pressure had administration of the drug ceased because of side effects. Twenty-two of these resistant patients had little fall in blood pressure. Labetalol can be used safely in severe resistant hypertension and is indicated when a thiazide and beta-blocking drug has failed to reduce blood pressure.

Comparison of piretanide and chlorothiazide in the treatment of cardiac failure

Piretanide, a diuretic that acts on the loop of Henle, was used to treat patients with cardiac failure. Over a three-day period it caused a significant dose related diuresis and weight loss. It was as effective as chlorothiazide in the control of cardiac failure and was well tolerated by the patients. Potassium loss was less than occurred with chlorothiazide. Its role in the treatment of cardiac failure requires further study and warrants further investigation. The study also showed that many patients with cardiac failure receive diuretic drugs which are not necessary.

The evidence that salt is an important aetiological agent, if not the cause, of hypertension

1. Salt intake and the incidence of hypertension correlate between populations. 2. Salt intake within a population may correlate with the incidence of hypertension. 3. Disorders that lead to retention of salt cause hypertension. 4. Modest salt restriction reduces blood pressure in many patients. 5. Reducing salt balance and preventing the compensatory rise in angiotensin II controls blood pressure in most patients. 6. Salt is the probable cause of the epidemic of hypertension in the Western world; this could be prevented by salt restriction.

Treatment of mild hypertension in elderly males

1. Males, born between 1900 and 1925, with mild hypertension have been treated for periods varying from 300 to 2000 days. 2. The life and death status of all patients (except two) was known on 1st November 1978. 3. A group of patients with mild hypertension receiving treatment based on a thiazide diuretic had a greater mortality than the other drug-treated group. 4. The increased mortality was caused by an increased number of myocardial infarcts. 5. Elderly male patients with mild hypertension probably have preexisting vascular disease and therapy should not automatically be started. If therapy is started, beta-adrenoreceptor-blocking drugs may be a preferred therapy.

Improved laboratory efficiency and diagnostic accuracy with new double-lumen-protected swab for for endometrial specimens

Intrauterine specimens were obtained from 22 patients with endometritis and 24 control patients following cesarean section by using both a new protected swab and a standard anaerobic swab. The protected swab improved the value of the direct smear and Gram stain, resulted in fewer false-positive cultures, better defined endometrial flora in patients with endometritis, and permitted major savings in laboratory personnel time and materials.

Treatment of mild hypertension

1. A total of 206 patients, elderly males with hypertension (diastolic blood pressure 95--110 mmHg) were followed for periods varying from 1 to 5 years, 107 patients with diastolic blood pressure less than 95 mmHg were followed over the same period, and 101 patients with diastolic blood pressure greater than or equal to 110 mmHg were also followed. 2. The mortality of each group and the effect of therapy for hypertension on mortality has been compared. 3. The incidence of myocardial infarct in the group treated with thiazide diuretics is greater than in the other groups. 4. It would appear unlikely that therapy will improve the prognosis in elderly people with mild hypertension.

The effect of labetalol in the treatment of severe drug-resistant hypertension

Twenty-two hypertensive patients from a large clinic, who were resistant to conventional therapy, were entered into this study. Most patients previously had received beta-blocking drugs, thiazide diuretics, alpha-methyl-dopa, or vasodilator drugs (hydrallazine or prazosin) which failed to control their blood pressure. The therapy with vasodilator drugs was discontinued, and the therapy with labetalol (a drug with both alpha-blocking and beta-blocking effect) was commenced. Subsequently, as the blood pressure came under control, other drugs that the patients were taking were also withdrawn. In 13 of the 22 patients, labetalol enabled the blood pressure to be controlled at acceptable levels. In six patients, the response was not considered to be sufficient to justify continuation of labetalol therapy. In three patients, the drug was withdrawn because of postural hypotension in one patient, intractable diarrhoea in another, and an allergic-type skin rash in the third. In certain patients, postural changes in blood pressure were observed, but this rarely produced symptoms. It is suggested that, if blood pressure control is not achieved with a thiazide diuretic and a beta-blocking drug, then labetalol should be introduced and the beta-blocking drug should be withdrawn.

A study of the interaction of catecholamines and antidiuretic hormone on water permeability and the cyclic AMP system in isolated papillae of the rat

The diffusional water permeability of collecting ducts in vitro and the cyclic A.M.P. content of isolated papillae were measured after exposure to different concentrations of antidiuretic hormone, isoproterenol and noradrenalin. Antidiuretic hormone 25 mu units/ml. caused a 25% increase in diffusional water permeability. This response was not affected by isoproterenol (10(-6) M) or noradrenalin (2 x 10(-6) M). Antidiuretic hormone 100 mu unit ml-1 caused a 50% increase in diffusional water permeability which likewise was not altered by isoproterenol or noradrenalin. Isoproterenol (10(-6) M) and noradrenalin (2 x 10(-6) M) had no significant effect on basal levels of diffusional water permeability. Isoproterenol had no significant effect on the tissue concentration of cyclic A.M.P. concentration induced by antidiuretic hormone. Noradrenalin (2 x 10(-6) and 10(-4)) had no significant effect on basal cyclic A.M.P. concentration. However, noradrenalin inhibited the stimulation of cyclic A.M.P. induced by antidiuretic hormone. This effect was inhibited by phentolamine. This study suggests that catecholamines do not alter water handling by a direct action on the water permeability of the kidney but probably exert their action through an effect of A.D.H. release.

Hypertension treated by salt restriction

31 patients with a diastolic blood-pressure between 95 and 109 mm Hg have been treated for two years with a regimen involving a moderate restriction of salt in the diet. The results are compared with those in a control group and in a drug-treated group. Salt restriction has reduced the diastolic blood-pressure by 7.3+/-1.6 mm Hg, a result similar to that in patients treated with antihypertensive drugs. In the untreated group the diastolic blood-pressure rose by 1.8+/-1.1 mm Hg. Most patients did not achieve the desired amount of salt restriction and a stricter adherence to the diet might have caused further falls in blood-pressure. Excessive salt intake is probably a major cause of the epidemic of hypertension in "civilised" countries and a reduction in salt intake may help to control the epidemic. In persons with a diastolic blood-pressure between 90 and 105 mm Hg salt restriction should be tried before drugs.

The effects of sodium chloride, urea and mannitol on the permeability in vitro fo rat papillary collecting ducts to THO, 14C-urea and 22Na

1. The diffusional permeabilities of collecting duct membranes to THO, 14C-urea and 22Na+ have been measured at different concentrations of urea, NaCl and mannitol. 2. In the absence of urea in perfusate and bath or in its presence in low concentrations, the diffusional permeability to urea was 2.0 (s.e.m. = 0.15, n = 58) micrometer s-1, compared with 0.87 (s.e.m. = 0.06, n = 29) microgram s-1 when 200 mmol/l urea was present. The permeability of the collecting ducts to THO or Na+ was not affected by the different urea concentrations. 3. High concentrations of sodium chloride increased the diffusional permeability of collecting ducts to water and urea but did not affect the diffusional permeability of the collecting duct to Na+. 4. Mannitol had effects similar to those of sodium chloride. 5. In all media tested there was an increase in THO and urea permeability when supramaximal amounts of antidiuretic hormone were added. The increases in the various media for each substance were similar, despite widely different starting permeabilities. 6. The results suggest that solutes and water move across collecting duct epithelium by several pathways that respond differently to various stimuli.

A simplified approach to the treatment of hypertension

A new beta-adrenoreceptor blocking drug (timolol) was used in two clinical studies. In the first double blind study administration of hydrochlorothiazide and timolol reduced the mean (formula: see text) blood pressure by 23 mm Hg, compared with a fall of nine mm Hg with administration of hydrochlorothiazide and a placebo. Plasma potassium (K+) levels fell with the administration of hydrochlorothiazide alone, but rose back to control values when patients were given timolol. In the second study (patient blind), Moduretic (hydrochlorothiazide, 50 mg and amiloride, 5 mg) and timolol were given once daily. The mean blood pressure fell by 20 +/- 2 mm Hg allowing hypertension to be controlled by this once-daily regimen; the control persisted throughout the day. Plasma potassium (K+) levels fell slightly after treatment with Moduretic, but the fall was not as great as with hydrochlorothiazide. Of the 65 patients who entered these studies, 35 had not been previously treated and had diastolic blood pressure between 105 mm Hg and 130 mm Hg. In 18 patients the diastolic blood pressure was reduced below 95 mm Hg after treatment with a diuretic alone, in 15 patients treatment with a diuretic and timolol (5 mg to 20 mg) reduced the diastolic blood pressure below 95 mm Hg. In two patients, the diastolic blood pressure was between 95 mm Hg and 100 mm Hg. The response achieved with a relatively simple therapeutic regimen that can be administered once daily suggests that the therapy of most hypertensive patients could be supervised by paramedical personnel.

Cinoxacin concentrations in plasma, urine and prostatic tissue after oral administration to man

Cinoxacin, a synthetic antibacterial compound, was given orally in a dose of 500 mg to 8 patients undergoing transurethral prostatectomy. The drug was well absorbed and the peak plasma level (mean 13.9 mcg/ml) occurred 1 or 2 hours after administration. Concentrations of cinoxacin in the urine reached a peak (mean 236.5 mcg/ml) 4 to 6 hours after dosing, and remained higher than the mean MIC for most common urinary pathogens for 12 hours after administration. The concentration of cinoxacin in prostatic tissue 2.5-4 hours after administration varied between 0.6 and 6.3 mcg/g. The individual variations were unrelated to the concurrent plasma level and appeared to be influenced more by inter-subject variation than by the physicochemical properties of the drug. In 1 patient the cinoxacin level was estimated in renal tissue (70.1 mcg/g), in muscle (12.6 mcg/g), and in perirenal fat (4.7 mcg/g).

Factors controlling the release of renin. A micropuncture study in the cat

Blood was collected by micropuncture from the efferent arteriole and superficial venules of the cat's kidney. Blood samples were also collected from the femoral artery and the renal vein. The blood renin concentrations (ng A1 m1-1 2h-1) in a basal state were 37.2 +/- 3.5 (S.E.M.) (n equal to 60) (artery), 32.5 +/- 5.2 [7] (efferent arteriole), 53.5 +/- 4(116) (superficial venule), 54.2+/- 5.4 (43) (renal vein). The corresponding values after haemorrhase were 389 +/- 98 (21), 345 +/- 115 (6), 963 +/- 208 (37), 907 +/- 290 (17), ng A1 m1-1 2h-1. The efferent arteriolar renin did not differ from that in the artery but the concentrations in superficial venular blood and renal vein were higher than arterial concentration. Thus renin entered the circulation between the efferent arteriole and the superficial venule. The blood renin concentration of different superficial venules at a steady arterial renin concentration varied markedly. Into certain venules there appeared to be little or no renin secretion, into others a marked renin secretion, suggesting a heterogeneity of renin secretion by the different nephrons. When the flow of tubular fluid to the macula densa of a group of nephrons was blocked, the renin concentration fell and was significantly less than the renin concentration in venules draining non blocked nephrons and less than in the renal vein. These results suggest that the juxtaglomerular apparatus of the nephrons do not release renin in a synchronous fashion. The release appears to be episodic and is inhibited when flow to the macula densa is ceased. This implies that a high sodium concentration at the macula densa stimulates renin release.

A role of frusemide in resistant hypertension

Five patients who were resistant to their antihypertensive drug therapy were admitted to hospital. Four had marked falls in blood pressure and an associated loss of weight. This fall in blood pressure was able to be repeated outside hospital by adding frusemide to their other drug therapy. Certain hypertensive patients become resistant to their antihypertensive therapy, owing to the accumulation of sodium. Thiazides may not have sufficient natriuretic properties to correct this accumulation. In these circumstances, frusemide may allow the hypertension to be controlled.

Effect of NaCl on composition and volume of cells of the rat papilla

The composition and volume of the cells of an isolated rat papilla were measured in media in which NaCl was varied from 150 to 600 mM; KCl, from 2 to 20 mM; or which contained mannitol, 300 mM. Change in NaCl from 150 to 600 mM reduced cell volume by 25%, increased cell Na+ content by 250% but had no significant effect on cell potassium concentration or content. Increases in K+ concentration in the media did not affect cell water or cell sodium, but the cell potassium rose by an amount approximately 3 times the increase in the medium concentration. Mannitol reduced cell volume; the cell content of sodium and potassium did not alter, but the concentration of Na+ and K+ altered reciprocally with the change in cell volume. Similar changes were observed with liver slices. This study indicated that papillary cells maintain osmotic equilibrium by the accumulation of sodium. This accumulation may influence the metabolic activity of the medullary and papillary cells.

The effect on blood pressure of beta-adrenoreceptor-blocking drugs given once daily

1. Blood pressure was controlled to the same extent whether propranolol or pindolol was given once or three times/day. 2. The anti-hypertensive action of beta-receptor-blocking drugs persisted for 36-48 h when administration ceased.

Optimal dose of a thiazide diuretic

In essential hypertension, 25 mg and 100 mg of chlorthalidone per day reduced blood pressure to a similar extent. The larger amount (100 mg per day of chlorthalidone) caused a greater reduction in extracellular volume and a larger rise in plasma renin activity and serum uric acid levels. Hypokalaemia was common with 100 mg per day of chlorthalidone, but was rarely seen in patients who took 25 mg per day, and neither dose caused total body potassium depletion. In the management of hypertension, 25 mg of chlorthalidone is the preferred dose as it produces most of the antihypertensive effects with only minor biochemical changes.

The effect of lithium on the permeability response induced in the collecting duct by antidiuretic hormone

The diffusional and osmotic water permeability of collecting ducts in isolated papillae of rats' kidneys were measured in papillae taken from normal and lithium pretreated rats. The diffusional water permeability of collecting ducts in papillae from normal rats in the absence of ADH was 4.1 +/- 0.2 (S.E.M.) (n = 18) muM s-1 increasing to 7.2 +/- 0.6 mum s-1 with ADH. Values obtained with lithium (10 mM) in the medium, perfusate or both and in papillae taken from lithium pretreated rats did not differ significantly from the above. The cyclic AMP content of the papillae taken from normal rats was 83 +/- 6 pm mg protein in the absence of ADH and increased to 196 +/- 12 (n = 13) with 500 mu units ml-1 ADH. Lithium 10 mM in the medium did not alter this response. Papillae from lithium pretreated rats had a similar basal level of cyclic AMP but the increment in a lithium (10 mM) medium after ADH was significantly less. These results indicate that the impaired water handling of lithium treated rats is probably not due to a failure of the membrane to increase its permeability to water after ADH. Though lithium does alter the production of cyclic AMP this is not believed to be important regarding any alteration in water permeability. We believe it is probable that lithium interferes with sodium chloride transport at some more proximal nephron segment thereby producing the syndrome of polyuria.

A study in vitro of the concentrating defect associated with hypokalaemia and hypercalcaemia

The diffusional water permeabilities of collecting ducts in the presence and absence of antidiuretic hormone have been measured in isolated papillae from normal, hypokalaemic and hypercalcaemic rats. In a similar in vitro situation the effect of antidiuretic hormone on the papillary content of cyclic AMP has been measured. The diffusional water permeability of collecting ducts in the absence of antidiuretic hormone did not differ significantly in papillae taken from the different groups of rats. The diffusional water permeability in the presence of ADH was 7.4 +/- 0.2 (S.E.M.) mum s-1 in collecting ducts taken from normal rats. In collecting ducts taken from hypokalaemic or hypercalcaemic rats the corresponding values were 5.9 +/- 0.3 and 5.8 +/- 0.5 mum s-1 respectively. This significant decrease (P less than 0.01) in the response to antidiuretic hormone would shift the point at which distal tubule fluid first attains isotonicity with the interstitium. If this shifts from cortex to medulla a greater amount of water enters the interstitium of the medulla and produces an impairment of maximal urinary concentrating ability and this defect could explain most of the observed results in hypokalaemic and hypercalcaemic. Cyclic AMP content of the tissue after the addition of ADH was reduced in papillae taken from hypokalaemic rats. This reduced activation of adenyl cyclase could be the mechanism responsible for the impaired response in water permeability but it is also possible that there is interference, with the chain of reactions mediating permeability changes, at a separate site.

The effect on blood pressure of beta-adrenoceptor blocking drugs administered once daily and their duration of action when therapy is ceased

The control of blood pressure achieved was similar whether pindolol or propranolol was given once or three times daily. When the drugs were ceased the antihypertensive effect lasted for longer than 24 h. There was no rebound hypertension. The full effect of the drug on blood pressure was seen within 24 h of its recommencement. Changes in blood pressure, pulse rate, and plasma renin activity occurred but these were not considered to be causally related. The response of plasma renin activity to posture was ablated when the patients were receiving beta-adrenoceptor blocking drugs.

Renal physiology

The kidney is composed of one million nephrons that function as a series of integrated units. The excretion of a wide range of natural and artificial compounds results from unselective filtration and specific reclamation of wanted substances. Active transport of weak acids and weak bases supplements this mechanism. In addition to its excretory function, the kidney has important endocrine and metabolic functions and influences the function and metabolism of most body systems. An understanding of renal function affords an explanation for many of the phenomena observed in renal disease.

The interrelationships between antidiuretic hormone, adenyl cyclase, tissue cyclic AMP and diffusional water permeability

1. Physiological concentrations of antidiuretic hormone increase diffusional water permeability but not measurable cyclic AMP content in the isolated papilla of the rat's kidney. 2. Theophylline (6 mM) increases diffusional water permeability and cyclic AMP content in the isolated papilla of the rat's kidney. 3. The increase in water permeability is detected with 5 muunits.ml-1 of ADH and is maximal with 50 muunits.ml-1. The same maximum was achieved with 6 mM theophylline. 4. Cyclic AMP and dibutyryl cyclic AMP both increase water permeability, but to a lesser extent than theophylline or ADH. 5. In the presence of theophylline, ADH causes a dose related generation of tissue cyclic AMP up to a dose of 2,000,000 muunits.ml-1. 6. Adenyl cyclase is increasingly activated by ADH up to doses of 2,000,000 muunits.ml-1. 7. These results suggest that while ADH activates the adenyl cyclase system and changes water permeability there are sufficient disparities to cast doubt on an exclusive role for cyclic AMP as the second messenger.

Renin secretion at the individual nephron level

Blood was collected from the descending aorta, from a renal efferent arteriole and from the renal vein of a rat. The renin concentrations of the blood samples were measured. The renal vein renin concentration was 673 +/- 81 (SE) ng ml-1h-1 which was significantly higher than the concentration in the aorta of 456 +/- 50 (SE) ng ml-1h-1. The concentration of renin in the renal efferent arteriole was significantly lower than that in the aorta. These observations imply that net renin secretion is a combination of two processes; removal between artery and efferent arteriole and entry between efferent arteriole and renal vein. It appears that renin is released into the interstitium and enters the circulation at the capillary level rather than being released into the afferent or efferent arterioles. This mode of secretion supports the suggestion that the renin angiotensin system may primarily work intra-renally rather than through the systemic circulation.

Sodium restriction and thiazide diuretics in the treatment of hypertension

In a group of hypertensive patients it has been shown that moderate sodium chloride restriction has a hypotensive effect that is similar to that produced by thiazide diuretics. Blood pressure changed in relation to body weight in individual patients, and appeared to correlate with their sodium balance. The more a patient was depleted of sodium, the lower was the blood pressure. The serum potassium level fell with the use of thiazide diuretics, but in this group of patients there was little change in total body potassium content. The fall in serum potassium level appeared to relate to a shift into the cells due to the accompanying alkalosis. Potassium supplementation appeared to have had little effect and was unnecessary for most patients who were given diuretics for hypertension. Amiloride corrected the alkalosis and restored the serum potassium level to normal.

Changes in plasma renin activity and blood pressure after acute and chronic administration of beta-adrenergic receptor-blocking drugs

1. Prindolol and propranolol chronically cause a fall in mean blood pressure and mean plasma renin activity, but no correlation was observed between the two variables. 2. The response of blood pressure to prindolol and propranolol was not predicted by the basal plasma renin activity. 3. Propranolol administered acutely caused the plasma renin activity to fall with no acute change in blood pressure, whereas prindolol caused the blood pressure to fall with no change in plasma renin activity. 4. The effects of beta-adrenergic-blocking drugs on plasma renin activity and blood pressure can be dissociated and it is unlikely that their hypotensive action is mediated through the renin-angiotensin system. 5. Basal plasma renin activity does not identify the patients who will respond to beta-adrenergic-blocking drugs.

Renin measurement in blood collected from the efferent arteriole of the kidney of the rat

Plasma renin could be detected in 16 nl of rat plasma by incubating at 50 degrees C, pH 6.2 with 20 mul of a rat renin substrate. In 60 nl samples it could be estimated and differences in concentration of 20% could be detected. Plasma renin concentration was measured in blood from the superficial efferent arterioles of a rat's kidney. The concentration of renin in different efferent arterioles of the same rat were similar. The renin concentration of efferent arteriolar blood was 361 plus or (-1)89 (S.D.) ng Al ml minus 1 (blood) hour (-1) which was not different from the renin concentration of simultaneously taken femoral artery blood (340 +/- 217). Plasma concentration can be measured in efferent arteriolar blood and will allow the control of renin secretion to be studied.