John P. Coghlan

Purification and cloning of a corpuscles of Stannius protein from Anguilla australis

The kidneys of teleost fish are associated with tissues containing secretory granules--the corpuscles of Stannius (CS). Electron microscopy indicates that the granules are of a proteinaceous nature and may represent hormones or enzymes of unrecognized physiological and biochemical function. In the present study, two-dimensional gel electrophoresis and electroelution was used to purify the major protein to homogeneity; it is approximately 32,000 Da in the reduced form and glycosylated. From the partial NH2-terminal sequence, a 75-mer oligonucleotide probe was synthesized and used to isolate a cDNA clone from which the complete amino acid sequence of the major CS protein was deduced. Polyclonal antibodies raised against CS homogenates were specific for the CS proteins (confirmed by immunohistochemistry). Hybridization histochemistry was used to confirm the location of the mRNA encoding the isolated protein. Incubation of CS homogenate with eel plasma or ovine renin substrate did not result in any angiotensin-like peptides whereas kidney homogenate did.

The granulated peripolar epithelial cell: a potential secretory component of the renal juxtaglomerular complex.

THE renal juxtaglomerular complex is conventionally considered to consist of the afferent and efferent glomerular arterioles, the macula densa of the distal tubule, and the interposed polar cushion region1. The afferent arteriolar wall contains myoepithelial cells characterised by the presence of multiple secretory-type cytoplasmic granules. It is widely accepted that such granules contain renin2, the hormone responsible for the production of angiotensin I from plasma renin substrate. We now report the finding of another potential secretory component of the juxtaglomerular complex, raising the possibility of unsuspected functional interactions in this region.

THE EFFECT OF ALDOSTERONE, CORTISOL, AND CORTICOSTERONE UPON THE SODIUM AND POTASSIUM CONTENT OF SHEEP'S PAROTID SALIVA*

Sodium depletion in the sheep results in a fall in parotid salivary sodium/potassium concentration ratio (Na/K) from a normal 25 to 40 (Na, 170 to 185 and K, 4 to 6 mEqper L) to as low 0.3 (Na, 40 and K, 133 mEqper L) (1, 2). Earlier work in this laboratory suggested that this reciprocal alteration in the concentration of salivary sodium and potassium was due predominantly to the simultaneous operation of 1) a fall in the salivary secretion rate and 2) an increase in the secretion of electrolyte-active adrenal steroids. If suitable allowance were made for the effects of variation in the parotid salivary secretion rate and the latency of the response, it was proposed that the salivary Na/K ratio could be used as an index of the release of electrolyte-active steroid into the circulation (2-5). Cortisol (6), corticosterone (6), and aldosterone (7-9) have been identified in sheep adrenal venous blood. In order to obtain a basis for evaluating the contribution of each of these components of the adrenal secretion to the fall in parotid salivary Na/K ratio observed during different physiological states, the effects of these steroids upon salivary Na and K were studied in a series of experiments in normal and adrenalectomized sheep.

Preoperative Lateralisation of Aldosterone-Producing Tumours in Primary Aldosteronism

Abstract A technique based on measurement of aldosterone in peripheral and left-adrenal venous plasma is described for the preoperative lateralisation of aldosterone-producing adenomas of the adren...

Can Excess Glucocorticoid, in Utero, Predispose to Cardiovascular and Metabolic Disease in Middle Age?

For many years, both human and animal studies correlated changes in behaviour of the young offspring with the degree of maternal stress or glucocorticoid exposure of the foetus/neonate. In the past ten years there has been overwhelming epidemiological evidence to suggest that growth retardation in utero is a very important risk factor for the development of cardiovascular and metabolic disease in adult life. More recently, it has been shown that one important, even key, determinant is the exposure of the foetus to excess glucocorticoid. Even a brief period (48 h) of dexamethasone exposure very early in pregnancy was able to programme permanently hypertensive adult sheep. Understanding how such programming works, and the underlying physiological changes that occur, provides one of the most exciting challenges in contemporary endocrinology and developmental biology.

Renin, Angiotensin II, and Adrenal Corticosteroid Relationships during Sodium Deprivation and Angiotensin Infusion in Normotensive and Hypertensive Man

The responses of plasma renin activity, plasma angiotensin II, plasma aldosterone, cortisol, and corticosterone to sodium deprivation and to angiotensin II infusion (100 ng/min) were measured in 8 normotensive patients and in 17 patients with essential hypertension. Following sodium deprivations, plasma renin activity rose from 0.513 ± 0.100 to 1.029 ± 0.124 ng/ml hour−1 in normotensive patients and from 0.406 ± 0.077 to 0.629 ± 0.059 ng/ml hour−1 in hypertensive patients. Plasma angiotensin II did not parallel changes in plasma renin activity: in normotensive patients plasma angiotensin II was unchanged by sodium deprivation (31.8 ± 6.0 compared with 30.1 ± 4.6 pg/ml), but in hypertensive patients it rose from 22.2 ± 3.4 to 36.4 ± 5.1 pg/ml. Plasma aldosterone rose equally in both groups following sodium deprivation (5.8 ± 1.3 to 15.3 ± 2.4 ng/100 ml for normotensive patients and 5.9 ± 1.4 to 14.4 ± 1.6 ng/100 ml for hypertensive patients) and angiotensin infusion (5.8 ± 1.3 to 10.4 ± 2.1 ng/100 ml in sodium-loaded normotensive patients, 15.3 ± 2.4 to 19.6 ± 3.6 ng/100 ml in sodium-deprived normotensive patients, 5.9 ± 1.4 to 11.4 ± 2.7 ng/100 ml in sodium-loaded hypertensive patients, and 14.4 ± 1.6 to 22.2 ± 2.6 ng/100 ml in sodium-deprived hypertensive patients). However, changes in endogenous plasma angiotensin II did not correlate with the rise in plasma aldosterone caused by sodium deprivation, and, despite much larger increases in plasma angiotensin II during angiotensin II infusion, plasma aldosterone showed smaller rises than those accompanying sodium deprivation. Plasma renin activity fell during angiotensin II infusion, in both groups of patients during both sodium loading and sodium deprivation, and, hence, the infusion constitutes a potent feedback inhibition of renin release in normotensive and hypertensive man. Plasma cortisol and corticosterone were unaltered by sodium deprivation but fell significantly with the angiotensin II infusion.

[DES-ASP1] angiotensin II in the sheep: Blood levels and its effect on plasma renin concentration

Abstract The present study describes an improved method for measuring angiotensin III in arterial blood. This was accomplished by SE-sephadex column to separate angiotensin II from angiotensin III prior to radioimmunoassay. The arterial concentration of angiotensin III measured before and after 24 to 48 hours sodium depletion by acute cannulation of parotid gland was 12.4 ± 1.7 fmol/ml (SEM, n=7) and 49.8 ± 10.3 fmol/ml (SEM, n=7) respectively. The arterial concentration of Val 4 -angiotensin III obtained from continuous infusion of Val 4 -angiotensin III at rates of 24 and 48 nmol/h in sodium deficient sheep were 245 ± 32.5 fmol/ml (n=6) and 330 ± 11.4 fmol/ ml (n=7) respectively. The clearance rate of exogenous Val 4 -angiotensin III in sodium deficient sheep after correction for endogenous level was calculated to be 140 ± 13.6 L/h (SEM, n=13). This was in the same order as Ile 5 -angiotensin II and Ile 4 -angiotensin III reported earlier in sodium replete sheep. Prolonged intravenous infusion of Val 4 -angiotensin III at a rate of 48 nmol/h in sodium- deficient sheep suppressed plasma renin concentration to the same extent as equimolar infusions of angiotensin II. This suggests that angiotensin III may inhibit renin secretion by a similar mechanism to angiotensin II.

The Structure and Biosynthesis of Epidermal Growth Factor Precursor

SUMMARY The structure of mouse submaxillary gland epidermal growth factor (EGF) precursor has been deduced from complementary DNAs. The mRNA is approximately 4800 bases and predicts prepro EGF to be a protein of 1217 amino acid residues (133×10 Mr). EGF (53 amino acid residues) is flanked by polypeptides of 188 and 976 residues at its carboxy and amino termini, respectively. The amino terminus of the precursor contains seven cysteine-rich peptides that resemble EGF. Towards the carboxy terminus is a 20-residue hydrophobic membrane spanning domain. The mid portion of the EGF precursor shares a 33 % homology with the low density lipoprotein receptor, which extends over 400 amino acid residues. These features suggest that EGF precursor could function as a membrane-bound receptor. RNA dot-blot analysis and in situ hybridization show EGF mRNA to be abundant in the submaxillary gland, kidney and incisor tooth buds. Lower EGF mRNA levels were found in the lactating breast, pancreas, small intestine, ovary, spleen, lung, pituitary and liver. In the kidney EGF mRNA was most abundant in the distal convoluted tubules. Analysis of EGF precursor biosynthesis in organ culture of the submaxillary gland and kidney showed differential processing of the precursor in the two tissues. In the submaxillary gland immunoreactive low molecular weight EGF was produced, but in the kidney the high molecular weight precursor was not processed. In the distal convoluted tubule of the kidney EGF precursor may act as a receptor that is involved in ion transport.

Angiotensin I, II, and III in sheep. A model of angiotensin production and metabolism.

SUMMARY The arterial and centra] venous concentrations of angiotensin I (AI), Val5-anglotensln II ([Val5]AII), and Val5-anglotensin III ([Val5]AIII(2-8)) were quantitatively determined in conscious sheep before and after sodium depletion. All three anglotenslns were elevated in blood with progressive sodium loss. During sodium deficiency the arteriovenous concentration ratios (A:V) of AI, [Val5]AII, and [Val5]AIII(2-8) were found to be 0.48 ± 0.03 (n - 9), 130 ± 0.05 (n - 16), and 1.52 ± 0.05 (n = 11) respectively. Intravenous infusion of [Val5]AII or [Val5]AIII(2-8) significantly elevated the A: V of respective angiotenslns, being 2.09 ± 0.28 (n - 5) for [Val5]AII and 2.2 ± 031 (n - 6) for [Val5]AIII(2-8). The blood clearance rates of exogenous [Val5]AII and [Vall]AIII(2-8) in sodium-depleted sheep were calculated to be 135 ± 15 liter/hr (n = 10) and 140 ± 13 liter/hr (n = 10) respectively. Based on these experimental data, a steady-state model of angiotensin metabolism was constructed.If it is assumed that endogenous arterial blood [Val5]AII and [Val5]AIII(2-8) cleared metabollcally at a similar rate as exogenous arterial blood angiotensins, it can be calculated that at steady-state 55% of the arterial [Val5]AII concentration was derived from the peripheral vascular bed. For [Val5]AIII(2-8), 63% of the arterial concentration was derived from the pulmonary circulation. The concentration of [Val5]AIII(2-8) in arterial blood was 42% of [Val5]AII.

Effect of Variations of Plasma Sodium Concentration on the Adrenal Response to Angiotensin II

The secretion rate of aldosterone was increased by infusion of valine-5-angiotensin II into the adrenal arterial blood supply of sheep. The dimensions of the increase in aldosterone output were inversely related to the control plasma concentration. This high aldosterone secretion was reduced substantially by concurrent adrenal infusion of concentrated NaCl solution which increased plasma sodium concentration by approximately 10 meq/liter. The reduction of aldosterone secretion occurred within 20 minutes. Angiotensin II infusion did not increase the secretion rates of cortisol or corticosterone. The significance of the finding that environmental sodium concentration has different effects on the aldosterone-stimulating action and the pressor action of angiotensin II is discussed.