Search PubMed⌕ Search

Biomedical subjects

T H Steele

Publications and source records attributed to T H Steele.

At least 19 recordsLinked to original sources
PubMed1990

Intrarenal angiotensin II inhibition influences the actions of atrial natriuretic peptide.

1. We previously found that kidneys isolated from salt-restricted rats were refractory to atrial natriuretic peptide compared with kidneys from salt-loaded rats. Because the intrarenal tissue renin-angiotensin system may modulate renal responses to atrial natriuretic peptide, we examined the effect of dietary NaCl loading on the responses of isolated perfused kidneys from normal rats to atrial natriuretic peptide, before and after the addition of angiotensin II receptor antagonists or angiotensin I converting enzyme inhibitors to the perfusate. 2. Atrial natriuretic peptide increased the glomerular filtration rate and sodium excretion of kidneys from NaCl-loaded rats. The addition of angiotensin receptor antagonists or converting enzyme inhibitors partially reversed the increments in glomerular filtration rate but not the increments in sodium excretion, leading to an increased fractional sodium excretion. In the absence of atrial natriuretic peptide, these agents did not affect glomerular filtration or sodium excretion. Kidneys from NaCl-restricted rats did not respond to atrial natriuretic peptide or to the inhibitors and antagonists, either separately or in combination. 3. After NaCl loading, the intrarenal renin-angiotensin system may augment the glomerular response to atrial natriuretic peptide while simultaneously inhibiting the natriuretic response to atrial natriuretic peptide. However, activation of the intrarenal renin-angiotensin system is not responsible for the refractoriness of kidneys from salt-restricted rats to atrial natriuretic peptide.

Angiotensin II↗
PubMed1979

Hypouricemia.

Explore the source record for details and available documents.

Body Water↗
PubMed1979

Mechanism of the uricosuric activity of ticrynafen.

Studies employing pyrazinamide, which have included the measurements of clearances of pyrazinamide and pyrazinoate, as well as of ticrynafen itself and its principal metabolite, have lent support to the hypothesis that ticrynafen inhibits the tubular reabsorption of both filtered and secreted urate by nephrons of the human kidney. The inhibition of the reabsorption of secreted urate by ticrynafen appears to be quantitatively important for eliciting its uricosuric and hypouricemic responses. Because the uricosuric and natriuretic responses correlate with urinary ticrynafen concentrations, the drug appears to inhibit tubular reabsorption after gaining access to tubule fluid. As a consequence of its extensive binding to plasma proteins, clearance data suggest that tubular secretion of ticrynafen is necessary for its action.

Diuretics↗
PubMed1979

Renal handling of urate: application to the action of tienilic acid.

The renal handling of urate is complex, involving its filtration by glomeruli, partial tubular reabsorption, tubular secretion and also the reabsorption of a portion of the secreted urate. Studies employing tienilic acid, both acutely and chronically, have suggested that this compound exerts its uricosuric action and decreases the plasma urate by inhibiting renal urate reabsorption. The magnitude of the natriuretic and uricosuric actions of tienilic acid are correlated with the concentration of drug in the urine. Crystal equilibration studies have suggested that tienilic acid should not predispose to crystalluria with either uric acid or monosodium urate.

Animals↗
PubMed1978

Renal response to phosphorus deprivation in the isolated rat kidney.

In order to study further the adaptation of inorganic phsophate (Pi) reabsorption during phosphorus depletion, Pi transport was measured at three perfusate Pi concentrations in isolated perfused rat kidney preparations, utilizing synthetic albumin-containing cell-free perfusate. With elevation of the perfusate Pi, phosphaturia was significantly less, and absolute Pi reabsorption was significantly greater in kidneys derived from phosphorus-deprived rats than in organs from nondeprived counterparts. Prior parathyroidectomy did not affect the transport of Pi by the isolated kidney preparation. Increasing the perfusate Pi did not diminish hypercalciuria in kidneys from phosphorus-deprived rats. The results indicate that the adaptive response in Pi reabsorption during phosphorus deprivation can be demonstrated independently of the composition of fluid perfusing the kidney. The mechanism underlying the adaptation, however, remains unclarified.

Animals↗
PubMed1978

Blunted norepinephrine natriuresis in the isolated spontaneously hypertensive rat kidney.

In order to characterize the relationship between blood pressure and renal sodium handling in the Kyoto spontaneously hypertensive rat (SHR), we did renal clearance and isolated perfusion studies in SHR and Wistar-Kyoto controls (WKY). Clearance studies revealed no differences in renal function between SHR and WKY. Isolated perfused kidneys from SHR demonstrated a diminished glomerular filtration rate (GFR) compared to WKY kidneys when both were perfused at normotensive pressures. Increasing the perfusion pressures to hypertensive levels by adjusting the perfusate flow rate increased both the GFR and sodium excretion to equivalent values. However, the addition of norepinephrine 15 ng/ml, to the perfusate resulted in a far greater natriuretic response in WKY kidneys than in SHR, despite equivalent increases in perfusion pressures, renal resistances, GFR, and filtration fractions. These results suggest that norepinephrine exerts a direct or indirect inhibitory action on renal sodium transport, and this effect is diminished in SHR kidneys. Additionally, abnormalities in renal sodium transport may play a role in the pathogenesis of hypertension in the SHR.

Animals↗
PubMed1978

Supersaturation of urine with uric acid and urate: response to a uricosuric diuretic.

In order to assess the possibility that treatment with the uricosuric diuretic ticrynafen (tienilic acid) could lead to UA or MSU crystalluria, the degree of urinary supersaturation with respect to these crystalloids was assessed in persons receiving the diuretic for 1 week, and the results were compared with similar data generated from the use of probenecid. Initially, only probenecid significantly increased the degree of urinary suspersaturation with respect to MSU, and after adjustment of urine pH values to 5.5, probenecid also increased the degree of urinary supersaturation with respect to nonionized UA. At a pH of 5.5, the urine was significantly more supersaturated with nonionized UA after a single dose of probenecid than after ticrynafen (tienilic acid). Ticrynafen never significantly affected the degree of urinary supersaturation with respect to UA or MSU. Neither agent affected small amounts of "colloidal" or "bound" urinary urate. Insofar as the degree of urinary supersaturation with these crystalloids predisposes to crystalluria and calculus formation, ticrynafen (tienilic acid) appears to present no increased risk.

Crystallization↗
PubMed1977

Bicarbonate-induced phosphaturia: Dependence upon the magnitude of phosphate reabsorption.

The acute effect of bicarbonate infusion on inorganic phsophate (Pi) reabsorption was determined in thyroparathyroidectomized (TPTX) rats stabilized on a high phsophorus diet. In the normophosphatemic state, bicarbonate did not affect Pi reabsorption significantly. On the other hand, after hyperphosphatemia was induced by phosphate loading, bicarbonate inhibited Pi reabsorption. In order to determin if eht aboslute level of plasma or filtered Pi was an improtant determinant of this phosphaturic action of bicarbonate during hyperphosphatemia, equivalent rates of Pi reabsorption were achieved after phosphate infusion in TPTX rats previously stabilized on a low dietary phosphorus intake, but at significantly lower plasma Pi concentrations and filtered Pi loads than in their high dietary phosphorus counterparts. Bicarbonate inhibited Pi reabsorption equivalently in both hyperphosphatemic groups, indicating that the magnitude of Pi transport itself was of importance in determining the inhibitory response to bicarbonate. In addition, the results suggest that transport mechanisms for bicarbonate and Pi may interact competitively.

Animals↗
PubMed1977

Renal response to phosphorus deprivation: effect of the parathyroids and bicarbonate.

Plasma inorganic phosphate (Pi) and Pi reabsorption were compared in intact and chronically thyroparathyroidectomized (TPTX) rats stabilized on a high or low-phosphorus diet after volume expansion with equivalent sodium bicarbonate or sodium chloride. Phosphate infusion after sodium chloride-loading resulted in greater hyperphosphatemia and diminished phosphaturia in TPTX rats than intact high-phosphorus rats. After sodium bicarbonate-loading, however, there was no difference between intact and TPTX high-phosphorus animals because bicarbonate inhibited Pi reabsorption extensively in both. In contrast, phosphate infusion after sodium chloride-loading in phosphorus-deprived rats elicited greater degrees of hyperphosphatemia and increased Pi reabsorption, irrespective of the presence or absence of the parathyroids. Sodium bicarbonate-loading inhibited Pi reabsorption significantly less in phosphorus-deprived rats than in high-phosphorus animals. Paradoxically, this inhibitory effect of bicarbonate in phosphorus depletion was greater in TPTX rats than in intact animals. Therefore, the presence of the parathyroids did not interfere with Pi reabsorption during phosphate infusion in sodium bicarbonate-loaded phosphorus-deprived rats. Sodium bicarbonate-loading interfered with Pi reabsorption most prominently in phosphorus-deprived rats when the parathyroids were absent.

Animals↗
PubMed1977

Diuretic-induced uricosuria: interaction with pyrazinoate transport in man.

We investigated the acute effect of an orally administered uricosuric natriuretic agent (SKF-62698) on renal urate transport in paired clearance studies in seven normal men. The participants received SKF-62698 on two separate occasions. Prior to the second study, each received pyrazinamide (PZA) in order to inhibit the tubular secretion of urate. Within 3 hours, SKF-62698 significantly decreased the plasma urate and trebled the rate of urate excretion in the studies without PZA. In contrast, after PZA pretreatment. SKF-62698 did not diminish the plasma urate appreciably and elicited only 60% of the previous increase in urate excretion. Sodium excretion quadrupled after SKF-62698, irrespective of the presence of PZA. Plasma concentrations of pyrazinoate, the renally active metabolite of PZA, were at levels previously shown in the chimpanzee to primarily inhibit the tubular secretion of urate. Therefore, intact tubular secretion of urate probably was necessary in order for SKF-62698 to elicit its maximum uricosuric response. SKF-62698 appeared to inhibit the tubular secretion of pyrazinoate, but the observed changes in urate transport could not be explained on that basis.

Adult↗
PubMed1976

Renal urate transport during variations in urate synthesis in the rat.

In order to determine the effect of intrarenal synthesis of urate upon the urinary urate excretion in the rat, we effected large changes in urate synthesis by increasing it with allopurinol. Hypoxanthine infusion increased plasma urate rapidly and also increased the urinary urate excretion and its renal clearance. However, when the plasma urate was maintained constant, hypoxanthine had no effect upon renal urate transport. Conversely, allpurinol infusion rapidly diminished the plasma urate, urinary urate excretion and its renal clearance. Again, the maintenance of a constant plasma urate concentration prevented any change in urate transport during allopurinol. The urinary degradative purine metabolic pattern was altered predictably by hypoxanthine and allopurinol. Assuming than any putative intrarenal component of urate synthesis would be affected predictably and consistently by hypoxanthine and allopurinol, these results suggest that changes in intrarenal urate synthesis are not an important determinant of urate excretion in the rat.

Allantoin↗
PubMed1976

Renal transport of urate during diuretic-induced hypouricemia.

The effect of two weeks administration of a uricosuric diuretic (SKF-62698) on renal urate handling has been examined in 11 normal men. Plasma urate concentrations had declined by more than 60 per cent after two weeks. Urate excretion per unit of glomerular filtration rate and urate clearance (Curate) per unit of glomerular filtration rate were increased after the administration of SKF-62698. The importance of intact tubular secretion of urate in producing these changes was assessed by administering pyrazinamide, an agent that curtails urate secretion, to each participant. The decrements in urate excretion and clearance produced by pyrazinamide both increased significantly, whereas the residual urate excretion rates and clearances not suppressible by pyrazinamide were only minimally altered by SKF-62698 treatment. These results suggest that the excretion of secreted urate was enhanced by prolonged administration of SKF-62698, probably secondary to the inhibition of postsecretory urate reabsorption. In addition, because the nonsuppressible urate excretion did not decline despite a 63 per cent reduction in the plasma urate, it is likely that the reabsorption of filtered urate also was impaired by SKF-62698.

Adult↗