Barbara R. Cole

Atriopeptins as Cardiac Hormones

P Needleman, SP Adams, BR Cole, MG Currie, DM Geller, ML Michener, CB Saper, D Atriopeptins as cardiac hormones ISSN: 1524-4563 Copyright

Atriopeptins: A family of potent biologically active peptides derived from mammalian atria

Extracts of rat atria are potent stimulators of sodium and urine excretion, and relax vascular and intestinal smooth muscle preparations. The structures of six biologically active peptides obtained from atrial extracts are reported here. Ion exchange chromatography of a low molecular weight fraction obtained by gel filtration of atrial extracts produced two natriuretic fractions: the first induced relaxation of intestinal smooth muscle strips only, whereas the second also relaxed vascular strips as well. From the first fraction four pure biologically active peptides obtained by reverse phase HPLC have been sequenced: the 21 amino acid peptide, designated atriopeptin I, and three homologs (des- ser1 -, des- ser1 -ser2-, and des- ser21 - atriopeptin I). From the second fraction two pure biologically active peptides were obtained, which had C-terminal extensions of atriopeptin I: atriopeptins II (23 amino acid residues) and III (24 residues), having respectively phe-arg and phe-arg-tyr C-termini. These results suggest that this family of six peptides, sharing the same 17 membered ring formed by an internal cystine disulfide, is derived from a common high molecular weight precursor.

Serum immunoglobulins in the nephrotic syndrome. A possible cause of minimal-change nephrotic syndrome.

To assess immunologic factors in the pathogenesis of idiopathic minimal-change nephrotic syndrome (INS), serum immunoglobulin concentrations were measured in 37 children with this syndrome and compared with those found in 36 with nephrotic syndrome secondary to chronic glomerulonephritis (CGN). Serum IgG and IgA levels were significantly reduced in nephrotic patients with either INS or CGN, IgG averaging 18.5 and 25.9 per cent of normal (P less than 0.001) and IgA 59.8 and 44.1 per cent of normal (P less than 0.01) respectively. Values increased after treatment of INS with prednisone, but mean values remained low. Serum IgM concentrations in INS averaged more than twice normal before, during, and after successful treatment with steroids. Patients with CGN did not have equivalent elevations of serum IgM. Thus, the primary defect in INS may be immunologic and could consist of deficiency in the T-cell function that mediates conversion of IgM synthesis to IgG synthesis.

Comparative vascular pharmacology of the atriopeptins.

The atriopeptins are potent relaxants of norepinephrine-constricted aortic strips or are dilators of renal blood vessels in isolated perfused rat kidneys that are constricted by norepinephrine. This vasorelaxant property of the atriopeptins requires the presence of phenylalanine arginine (i.e., atriopeptin II, III, or ser-leu-arg-arg atriopeptin III) residues in the carboxy terminus which are considerably more effective than atriopeptin I (the 21 amino acid peptide which lacks the phe-arg C-terminus) or the core peptide (residues 3–19). However, these artificially in vitro precontracted preparations do not accurately predict the vascular effectiveness of the atriopeptins in intact rats. Intravenous administration of the atriopeptins (including atriopeptin I) to anesthetized rats produces concentration-dependent hypotension, a selective decrease in renal resistance in low doses (determined with microspheres), and pronounced diuresis. At higher doses, atriopeptins increase blood flow in other vascular beds. On the other hand, in the anesthetized dog, injection (intraarterially) of the phe-arg-containing peptides produces a concentration- dependent increase in both renal blood flow and sodium excretion, whereas atriopeptin I is inactive. Although there is a species difference in responsiveness to atriopeptin I, these data demonstrate a direct correlation between the renal vasodilation and diuresis produced by this novel family of atrial peptides.

Living-unrelated renal transplantation provides comparable results to living-related renal transplantation: A 12-year single-center experience

BACKGROUND The increasing success of renal transplantation is paralleled by the increased size of the waiting list. Efforts to increase the donor pool have included the use of living-unrelated kidney donors (LURDs). METHODS During a 12-year period our center performed 309 transplantation from living donors; 279 patients received living-related donor (LRD) transplants, and 30 patients received LURD transplants. During the same period 543 patients received cadaveric renal donor transplants. A total of 86.7% of LURD transplants were spousal transplants. A total of 29% of the patients who received LRDs were human leukocyte antigen-identical with their donors and 53% were haploidentical, versus 0 human leukocyte antigen-identical or haploidentical in the LURD group. RESULTS Twenty-seven (90%) Of 30 LURD recipients are alive, as are 240 (86%) of 279 LRD recipients. Mean current creatinine is 1.6 mg/dl for the LURD group and 1.7 mg/dl for the LRD group Kaplan-Meier 1- and 5-year graft survival was 94.9% and 82.9% for the LRD group, 93.1% and 85.9% for the LURD group (p = not significant), and 84.6% and 70.7% for the cadaveric renal donor group (p < 0.05). CONCLUSIONS LURD patient and graft survival is comparable to LRD transplants despite inferior human leukocyte antigen matching. LURD transplant survival is superior to that of cadaveric renal donor transplants. LURDs are an excellent but underused source of organs for renal transplant recipients.

RENAL TRANSPLANTATION FOR SYSTEMIC LUPUS ERYTHEMATOSUS AND RECURRENT LUPUS NEPHRITIS: A SINGLE-CENTER EXPERIENCE AND A REVIEW OF THE LITERATURE

Prior to 1975 patients with systemic lupus erythematosus were generally not considered candidates for renal transplantation because of concern that immune complex deposition would rapidly destroy the allograft. However, recent evidence suggests that good patient and graft survival rates can be achieved comparable to other renal diseases. Between September 23, 1963 and July 31, 1990, 1070 renal transplants were performed at Washington University Medical Center (WUMC). During this period, 14 patients with SLE (12 female and 2 male) received 16 renal transplants (7 living-related donor [LRD], 1 living-unrelated donor [LURD], and 8 cadaver [CAD]). The mean age at the time of the first transplant was 32.5±10.3 years. The duration of disease prior to transplant was 88.0±45.9 months and the duration of hemodialysis prior to transplant was 36.0± 33.7 months. Of these patients, 7/14 (50%) had negative and 3/14 (21%) positive SLE serology pre- and post-transplant, 3/14 (21%) had negative serology pretransplant that became positive posttransplant, and 1/14 (2%) was positive pretransplant and became seronegative posttransplant. Patient survival was 92.8% (13/14), and of the 16 kidneys transplanted 62.5% (10/16) are still functioning with a mean follow-up period of 43.7±45 months. The current mean serum creatinine was 1.4± 0.26 mg/dl. One noncompliant patient developed recurrent lupus nephritis bringing the total number of cases reported in the literature to seven. The present study demonstrates that patients with SLE can be transplanted with excellent patient and graft survival and function and a low rate of recurrent lupus nephritis. From a review of the literature, there appears to be an association between positive SLE serology pre- and posttransplant and recurrent lupus nephritis.

Atriopeptin release from the isolated perfused rabbit heart

Mammalian atrial extracts have been shown to contain bioactive peptides which exert natruiretic, diuretic, and smooth muscle relaxant effects. These extracts include several low molecular weight (less than 5,000 Mr) atrial peptides (atriopeptins) which exhibit identical sequences over a central core region which are derived from the high molecular weight peptide (atriopeptigen) precursor which has been purified and sequenced. In the current study we found that extracts of rabbit atria possess both high and low molecular weight bioactive atrial peptides, however, the coronary venous effluent obtained from the isolated perfused rabbit heart only contained the low molecular weight peptide. This trypsin labile activity causes a dose-dependent relaxation of rabbit aorta and chicken rectum assay strips. Separation of the bioactivity with gel filtration chromatography and reversed phase HPLC indicates the heart releases a single substance similar to atriopeptin III. There was no evidence that atriopeptigen was released from the isolated perfused rabbit heart. We suggest that atriopeptigen is proteolytically processed in the atria to an atriopeptin which is subsequently the released form of the atrial peptide.

Atriopeptins: potential mediators of an endocrine relationship between heart and kidney

Abstract Homeostatic regulation of fluid and electrolyte balance is essential for survival. The kidney plays a primary role in determining the composition and volume of body fluids. Although numerous factors which regulate this homeostatic balance have been analysed, the humoral control of sodium excretion has been elusive. In this review Philip Needleman and his colleagues deal with the very recent identification of a novel family of peptides - atriopeptins I, II and III - present in the heart that have the capacity to modulate renal and vascular function. They also discuss the future.

The Treatment of Severe Glomerulopathies in Children Using High Dose Intravenous Methylprednisolone Pulses

Thirty-five patients, 29 with severe proliferative glomerulonephritis and six with either steroid resistant or steroid dependent nephrotic syndrome, were treated with high dose bolus infusions of methylprednisolone (pulses) followed by prednisone given orally in more conventional doses for 6 mo or longer. Twenty-one of the 29 patients with severe proliferative glomerulonephritis had sustained improvement in renal function after treatment. In addition, pulse treatments reduced proteinuria and urine sediment abnormalities in these patients. Those who did not respond had a long duration of disease before receiving pulse therapy. Five of six patients with the nephrotic syndrome had reduction in proteinuria and three of these patients entered prolonged remission after treatment. Few side effects occurred with pulse therapy. Our observations suggest that the use of steroid pulses may limit or prevent long-term major loss of renal function in many patients with severe proliferative glomerulonephritis. It may be effective also in treatment of some patients with steroid refractory or frequently relapsing nephrotic syndrome. This therapeutic approach deserves continuing evaluation.

Familial renal adysplasia

Renal dysplasia and agenesis as isolated findings are usually considered sporadic, noninherited abnormalities. We report three kindreds with familial renal adysplasia. Two or more children were affected in each of the families and at least one member--whether proband, sibling, or parent--had a clinically silent anomaly. Normal kidneys in the parents did not preclude the occurrence of renal adysplasia in more than one child. The empiric risks for offspring and first-degree relatives were 50% and 25%, respectively, suggesting a strong genetic factor such as a major dominant gene with variable expression. Because the disease appears to be genetic in some cases of renal adysplasia, careful screening of the probands family, subsequent children, and pregnancies is important for the purpose of accurate genetic counseling.