Studies on the role of platelet-activating factor in blood pressure regulation.

Circulating levels of 1-O-hexadecyl-2-acetyl-sn-glycero-3-phosphocholine (C16PAF) in human subjects were measured by gas chromatography/mass spectrometry using negative ion chemical ionization. The mean (+/- S.D.) circulating C16PAF levels in patients with essential hypertension (18.1 +/- 5.3 pg/mL, n = 16) were not significantly different from those in normotensive subjects (17.2 +/- 7.2 pg/mL, n = 14). During a salt balance study, high salt intake (20 g/day) significantly increased the circulating level of C16PAF, and changes in circulating C16PAF significantly and positively correlated with changes in mean arterial blood pressure (r = 0.47, p less than 0.05). Changes in C16PAF also correlated with changes in creatinine clearance (r = 0.55, p less than 0.05), but did not correlate with changes in plasma sodium concentration, plasma chloride concentration and plasma volume. An intravenous injection of 50 micrograms of human atrial natriuretic peptide (hANP) decreased circulating C16PAF levels from 20.0 +/- 2.7 to 13.9 +/- 2.4 pg/mL of blood (n = 10, p less than 0.01) in healthy subjects. The data appear to indicate that C16PAF levels are changed by salt intake-induced mild increase in blood pressure, and that hANP may be an endogenous factor which lowers circulating C16PAF.

Production and characterization of antibodies to ouabain.

Two monoclonal antibodies (249F8 and 278A9) to ouabain were produced by somatic cell fusion. They reacted in dose-dependent manners with ouabain and digoxin. These antibodies were supposed to recognize the partial structure important for cardiac compounds to show their pharmacological activity, Na+, K(+)-ATPase inhibition in a competitive mode against K+. These monoclonal antibodies may be useful for the immunochemical isolation, the structural elucidation, and the quantitative measurement of putative endogenous digoxin-like factors.

Production of anti-platelet-activating factor antibodies by the use of colloidal gold as carrier.

Polyclonal and monoclonal antibodies to platelet-activating factor (PAF) were produced, by use of colloidal gold as the hapten carrier. These polyclonal (R88-09) and monoclonal (602 B11) antibodies both reacted with PAF, lysoplatelet-activating factor (lyso PAF), and L-alpha-lysophosphatidylcholine, palmitoyl (lyso PCP), but did not react with phosphorylcholine chloride (PCC). Their affinities were higher for PAF than lyso PAF and lyso PCP.

Autoimmune neutropenia with anti-neutrophil autoantibody associated with Sjögren's syndrome.

A 74-year-old man developed neutropenia in association with Sjögren's syndrome. The peripheral neutrophils in his blood decreased to 210/mm3 (total white blood cell count 2,100/mm3). Bone marrow examination showed an increase in the number of neutrophil precursors. The presence of anti-neutrophil autoantibody (ANAB) in his plasma was determined by an enzyme-linked immunosorbent assay. Prednisolone therapy resulted in an increase in the neutrophil count and a decrease in the ANAB titer. However, when the daily dose of prednisolone was decreased, the neutrophil count gradually decreased, and the ANAB titer increased again. These results suggest that neutropenia in this patient was caused by ANAB, and ANAB could be the result of autoimmune disorders associated with Sjögren's syndrome.

[A case of recessive dystrophic epidermolysis bullosa associated with dwarfism with special reference to pathophysiological role of growth hormone].

Epidermolysis bullosa is a group of disorders whose common primary feature is the formation of blisters following trivial trauma. Recessive dystrophic epidermolysis bullosa (RDEB), a subtype of epidermolysis bullosa, is frequently associated with growth retardation. This growth retardation has been reported to be caused by trophopathy following protein loss through skin lesions. Endocrine disorders as the cause of growth retardation in RDEB have not been clearly described. An 11-year-old female had a typical RDEB with dwarfism. Her height was 125 cm and weight was 21 kg, both of which were 2.5 SD below the average. The skin lesions were generalized and probably caused by undernourishment, infection, and blood loss through the skin. However, her serum albumin was at the lower normal limit, and the rapid turnover proteins were slightly decreased. Endocrinological examinations revealed that all the basal levels of pituitary, thyroid, and adrenal hormones were normal. Results of the exercise test, the insulin tolerance test, and the growth hormone-releasing factor test indicated the presence of hypothalamic disorder in secretion of growth hormone. This is the first report of RDEB in which hypothalamic disorder in growth hormone secretion was investigated. On the other hand, growth hormone is known to be involved in collagen metabolism, and a decrease in collagen fibrils and an increase in collagenase activities are found in the skin of RDEB. This implies that this hypothalamic disorder in growth hormone secretion may be involved in the pathophysiology of both dwarfism and the skin lesions in RDEB.

Dietary salt, blood pressure and circulating levels of 1-O-hexadecyl-2-acetyl-sn-glycero-3-phosphocholine in patients with essential hypertension.

The effects of dietary salt on circulating levels of 1-O-hexadecyl-2-acetyl-sn-glycero-3-phosphocholine (C16 PAF) in patients with essential hypertension were studied by gas chromatography/mass spectrometry with negative ion chemical ionization. Circulating levels of C16 PAF in patients with essential hypertension (18.1 +/- 5.3 pg/ml, n = 16) were not changed compared with those in normotensive subjects (17.2 +/- 7.2 pg/ml, n = 14). Although changes in circulating levels of C16 PAF were small with changes in dietary salt, net changes in circulating C16 PAF levels significantly and positively correlated with net changes in mean arterial blood pressure (r = 0.47, P less than 0.05). Changes in C16 PAF levels also correlated with changes in creatinine clearance (r = 0.55, P less than 0.05). However, changes in C16 PAF levels did not correlate with changes in plasma sodium concentration, plasma chloride concentration and plasma volume. These results indicate that C16 PAF plays an antihypertensive role and this may be reflected as small changes in circulating levels of C16 PAF.

[Graves' disease with markedly elevated serum immunoglobulin E].

A 37-year-old female with Graves' disease was reported. An abnormally high concentration of serum IgE was observed by radioimmuno-sorbent test before treatment. Laboratory findings showed no evidence of atopic diseases or other known diseases with hyperglobulinemia E. There is no reported case of Graves' disease associated with remarkably elevated plasma IgE level. In the present patient, a further elevation of serum IgE concentration was observed when the dose of methimazole reached about 500 mg in total. Allergic mechanism may be the cause of this phenomenon. Serum IgE level was decreased gradually after replacement of methimazole by propylthiouracil. IgE level was not parallel with thyroid functions, and even when her thyroid function was normalized after subtotal thyroidectomy, IgE concentration was still increased around 900 IU/ml. The mechanism of hyperglobulinemia E in this case was discussed.

High plasma levels of cortisol in patients with senile dementia of the Alzheimer's type.

Plasma cortisol levels and other factors including thyroid hormone in patients with Alzheimer's type (n = 10), vascular type (n = 10) or mixed type (n = 10) senile dementia were compared with those in non-demented senile controls (n = 10). Plasma cortisol levels at 8:00 a.m. in Alzheimer's type dementia and mixed type dementia were 17.3 +/- 4.3 micrograms/dl (mean +/- SD) and 15.6 +/- 2.3 micrograms/dl, respectively. These values were significantly higher (p less than 0.005 and p less than 0.01) than those found in the control subjects (12.0 +/- 3.1 micrograms/dl). Plasma cortisol levels in vascular-type dementia (14.4 +/- 6.3 micrograms/dl) did not differ significantly from those in the controls. Plasma ACTH in senile dementia of the Alzheimer's type was lower, but not significant as compared with that in normal controls. In three subgroups of senile dementia and normal controls, plasma cortisol levels inversely correlated significantly with the degree of cognitive function. Plasma levels in TSH-thyroid system and blood pressure did not show any significant change in three types of senile dementia. These data suggest that senile dementia of the Alzheimer's type accompanies relatively and primarily high plasma cortisol levels and this may associate with cognitive dysfunction in Alzheimer's type senile dementia.

Splenomegaly in Papua New Guineans and in Japanese living in Papua New Guinea: report of research and exchange program of Osaka University with the South Pacific region.

Sizes of spleen and liver were studied by measuring spleen index calculated by multiplying the maximal length by the maximal width of the spleen and liver length at right mid-clavicular line below the costal margin using ultrasonography in 26 Papua New Guineans and in 25 Japaneses living in Papua New Guinea. In Papua New Guinean, spleen index and liver length were 77.4 +/- 9.9 cm2 and 5.4 +/- 0.7 cm, respectively. Their spleen index correlated inversely (p < 0.05) with hemoglobin level. In Japanese, spleen index and liver length were 24.5 +/- 2.1 cm2 and 0.8 +/- 0.3 cm, respectively and spleen index correlated positively with the duration of stay in Papua New Guinea (p < 0.05). These results indicate that the clinical and subclinical infections acquired in P.N.G. may play some role on the development of splenomegaly. Malaria is the prime suspect for the high prevalence of observed splenomegaly in both studied groups.

Partial purification and properties of a plasma ouabain-like inhibitor of Na+, K+-ATPase in patients with essential hypertension.

Plasma levels of an ouabain-like inhibitor of Na+,K+-ATPase were higher in patients with essential hypertension compared with normal levels. The ouabain-like inhibitor was correlated significantly with blood pressure and was increased by a high-salt diet. The substance was partially purified by high performance liquid chromatography which revealed lipid-like properties, but the elution time was different from that of free unsaturated fatty acid on silica-gel high performance liquid chromatography. Its molecular weight was 600 or less, as estimated by high performance liquid chromatography with an HSG-15H column. The ouabain-like substance inhibited Na+, K+-ATPase in competition with KCl and showed positive ouabain-like immunoreactivity, whereas lysophosphatidylcholine was a non-competitive inhibitor. The ouabain-like substance was unstable at room temperature and decomposed to smaller molecular compounds which did not inhibit Na+, K+-ATPase. The inhibitory fraction gave a positive thiobarbituric acid reaction test. The mobility of the ouabain-like inhibitor on silica-gel thin-layer chromatography was different from that of prostaglandins and arachidonic acid. These results indicate that the plasma ouabain-like inhibitor of patients with essential hypertension is a lipid which is different from free fatty acid or lysophosphatidylcholine, and may be an unstable peroxide.

Platelet-activating factor and anti-platelet-aggregating factor in acute reduction of blood pressure following percutaneous transluminal renal angioplasty in patients with renovascular hypertension.

The mechanism of the acute fall of BP following percutaneous transluminal renal angioplasty (PTRA) was studied in four patients with renovascular hypertension caused by fibromuscular dysplasia. One hour after PTRA, systemic blood pressure and plasma renin activity in the ipsilateral renal venous blood decreased significantly (P less than 0.05), but the plasma noradrenaline level in ipsilateral renal venous blood increased significantly (P less than 0.05). At the same time, a platelet-activating factor (PAF) and an unidentified factor that inhibited the aggregation of rabbit platelets induced by PAF, arachidonic acid or ADP were detected in the ipsilateral renal venous blood, but were not found in the contralateral renal venous blood. Plasma noradrenaline level in cubital venous blood decreased significantly (P less than 0.05) after 24 hours as compared with that before PTRA and BP also maintained the normal level. These results suggest that the reduction in plasma renin activity is associated with the acute reduction in BP following PTRA. PAF and an unidentified factor blocking the aggregation of platelets may be involved in ipsilateral renal venous blood following PTRA in patients with renovascular hypertension. The reduction in plasma noradrenaline level is an additional mechanism involved in maintaining normal BP following PTRA in the late stage.

Normalization of high plasma level of ouabain-like immunoreactivity in primary aldosteronism after removal of adenoma.

Plasma ouabain-like immunoreactivity, which has been supposed to be associated with hypertension, was significantly higher in five patients with primary aldosteronism than in age-matched normotensive subjects. High plasma levels of ouabain-like immunoreactivity decreased to normal after removal of adenoma. Extracts of adenoma tissue did not contain any apparent ouabain-like immunoreactivity. Anti-ouabain antibody used in this study did not cross-react with aldosterone, cortisol, corticosterone, arachidonic acid or lysophosphatidylcholine. Hypertension, hypokalemia, a high plasma aldosterone level and low plasma renin activity were also normalized after surgery. These results indicate that hyperaldosteronism induces the high plasma level of ouabain-like immunoreactivity and this is associated in part with high blood pressure (BP) in primary aldosteronism.

Changes in plasma lipids and uric acid with sodium loading and sodium depletion in patients with essential hypertension.

The short-term effects of manipulating dietary salt intake on plasma levels of cholesterol, lipoproteins and uric acid were studied in two groups of patient with essential hypertension. With dietary salt restriction in 8 patients (10 g to 2 g salt/day for five days), plasma total cholesterol, esterified cholesterol, beta-lipoprotein, low density lipoprotein and uric acid rose significantly. With salt repletion (2 g salt/day to 20 g/day for five days) in 17 patients, plasma total cholesterol, esterified cholesterol, beta-lipoprotein, low density lipoprotein and uric acid fell significantly. Total/HDL cholesterol ratio increased significantly with salt restriction and decreased significantly with repletion. However, very low density lipoprotein, HDL-cholesterol, triglyceride, phospholipid, chylomicron and non-esterified fatty acid were not influenced by the changes in salt intake. These results indicate that the severe restriction of dietary salt raises plasma cholesterol and uric acid levels in patients with essential hypertension in the short term.

Endogenous platelet-activating factor and anti-platelet-activating factor in patients with renovascular hypertension.

Renovascular hypertension is relieved by percutaneous transluminal renal angioplasty. In four patients with renovascular hypertension, platelet-activating factor (PAF) was found to be released into the ipsilateral renal venous blood after percutaneous transluminal renal angioplasty, but was not found in the contralateral renal venous blood following this procedure. Anti-platelet-activating factor with a lipid-like property was also found, and its polarity was slightly lower than that of PAF judging by its behavior on thin layer chromatography. Anti-platelet-activating factor completely blocked the aggregation of rabbit platelets induced by PAF, ADP or arachidonic acid. These results indicate that PAF and anti-platelet-activating factor are released into renal venous blood following percutaneous transluminal renal angioplasty in patients with renovascular hypertension.

Increase in plasma ouabainlike inhibitor of Na+, K+-ATPase with high sodium intake in patients with essential hypertension.

Changes in plasma levels of Na+, K+-ATPase inhibitors with salt loading were studied in eight patients with essential hypertension. By improving the assay method of Na+, K+-ATPase inhibitors to distinguish ouabain and vanadate, two types of inhibitors were detected in the plasma of patients with essential hypertension: One was ouabainlike and the other was nonouabainlike. The ouabainlike inhibitor was detected at low KCl concentrations (0.1 mM) in the assay buffer, and the nonouabainlike inhibitor was detected at a high KCl concentration (10 mM). By increasing dietary sodium chloride from 2 g/day for 5 days to 20 g/day for 6 days, systolic blood pressure increased significantly from 122 +/- 3.9 to 138 +/- 3.8 mmHg (p less than 0.005), whereas plasma renin activity decreased significantly from 3.9 +/- 0.8 to 0.8 +/- 0.3 ng/ml/hr (p less than 0.002). Under these conditions, the ouabainlike inhibitor increased significantly from 6.2 +/- 3.9% to 30.5 +/- 5.9% inhibition (p less than 0.005), after increasing dietary sodium. Furthermore, plasma level of the ouabainlike inhibitor correlated significantly with both systolic blood pressure (p less than 0.05) and daily urinary sodium excretion (p less than 0.01). In contrast, the plasma nonouabainlike inhibitor did not change with high sodium intake and did not correlate with blood pressure and daily urinary sodium excretion. These findings suggest that a ouabainlike inhibitor is involved in the maintenance of high blood pressure induced by high sodium intake in patients with essential hypertension. The role of the nonouabainlike inhibitor in blood pressure regulation is still unknown.

Ouabain-like and non-ouabain-like factors in plasma of patients with essential hypertension.

Circulating inhibitor of Na+,K+-ATPase and ouabain-like immunoreactivity were studied in patients with essential hypertension. In the plasma of patients, two types of Na+,K+-ATPase inhibitors (ouabain-like and non-ouabain-like inhibitors) and ouabain-like immunoreactivity were detected. Ouabain-like inhibitor was clearly detected at a low KCl concentration (0.1 mM) in the assay buffer, and non-ouabain-like inhibitor was detected at a high KCl concentration (10 mM). The plasma level of ouabain-like inhibitor correlated significantly with that of ouabain-like immunoreactivity (p less than 0.001) and with a mean blood pressure (p less than 0.01). The plasma level of non-ouabain-like inhibitor was not correlated with the levels of either ouabain-like immunoreactivity or mean blood pressure. The level of plasma ouabain-like inhibitor did not correlate with that of plasma non-ouabain like inhibitor. Both ouabain-like inhibitor and ouabain-like immunoreactivity in the plasma of patients with essential hypertension were significantly higher than those in normotensive subjects, but the plasma level of non-ouabain-like inhibitor in patients with essential hypertension was not higher than that in normotensive subjects. These results suggest that the plasma from patients with essential hypertension contains ouabain-like factor(s) which is important to maintain the high blood pressure.

The hypotensive effect of captopril is not mediated by renal medullary lipids.

The role of renomedullary lipids in the hypotensive effect of captopril was studied in spontaneously hypertensive rats, one-kidney, one clip hypertensive rats and two-kidney, one clip hypertensive rats using inhibitors of acetyl glyceryl ether phosphorylcholine and prostaglandins, and chemical medullectomy. Our experiments indicate that it is unlikely that renomedullary lipids contribute to the hypotensive action of captopril.