Insulin binding and its action in adipocytes of hyperthyroid and hypothyroid rats

The studies of the effects of thyroid hormone on insulin secretion and glucose metabolism have been made, but the results have been controversial. In order to evaluate the effects of thyroid hormone at the cellular level, insulin binding and insulin-induced lipogenesis in isolated rat epididymal fat cells were studied in control, hyperthyroid and hypothyroid rats. Hyperthyroidism was induced by daily intraperitoneal injection of sodium L-thyroxine and hypothyroidism by a single injection of ¹³¹I. The adipocytes were isolated by treatment of collagenase as originally described by Gliemann (1967). The results were as follows: 1) The fasting serum insulin levels of hyperthyroid (21.6 ± 3.7 uU/ml) and hypothyroid groups (20.5 ± 7.0 uU/ml) were not different from the value of control (23.1 ± 11 uU/ml). The fasting blood glucose level of hypothyroid group (164.9 ± 12.0 mg/dl) was higher than the values of the controls (148.2 ± 13.2 mg/dl) or the hyperthyroid group (147.0 ± 12.5 mg/dl), (p<.005). 2) The specific ¹²⁵I-insulin binding of the hyperthyroid group was not different from the value of the controls, but the value of the hypothyroid group was higher than the value of the controls (p<.005). 3) The insulin receptor concentration of the hypothyroid group (1.09 ± 0.02 ng/0.5×10⁵ cells) was higher than the value of the controls (0.72 ± 0.01 ng/0.5×10⁵ cells) or the hyperthyroid group (0.79 ± 0.02 ng/0.5×10⁵ cells), (p<.05). 4) The average affinities of the receptors in all groups showed an inverse correlation with the insulin concentration. The average affinity of the hypothyroid group was higher than the value of the control or the hyperthyroid group. 5) Insulin-induced lipogenesis was reduced proportionately in all insulin concentrations in both the hyperthyroid and hypothyroid groups compared with the dose-response curve of the control group. The maximal amount of lipogenesis of the hyperthyroid and hypothyroid groups were 63.4% (p<.05) and 32.3% (p<.005) of the controls, respectively. These studies suggest that thyroid hormone may regulate the concentration of insulin receptors, and altered thyroid states reduce insulin-induced lipogenesis in the adipocyte at postreceptor levels.

Percutaneous endoscopic gastrostomy for enteral nutrition

From January to October, 1986, at Wonkwang University Hospital in Iri, percutaneous endoscopic gastrostomy(PEG) was attempted in 26 patients and was successful in 24. This study was designed to review the technique and to evaluate the efficacy of PEG. The mean operation time was 22 minutes (range: 14 to 42 minutes). After feeding started, early positive nitrogen balance was achieved in all patients. All gastrostomies functioned well throughout the patient’s survival with the longest functioning at 10 month. There were no procedure-related deaths, and morbidity was lower and less severe as compared with large-bore nasogastric tube feeding. Complications included minor wound infection in two patients, stomal growth in one patient, leaks around the tube in two patients, and intraperitoneal leak in one patient. No patient developed aspiration pneumonia or required laparotomy for complications from PEG. The gastrostomy tube was easily removed endoscopically when treatment was completed. Feeding via a large-bore tube increased the risk of aspiration pneumonia (72%) and the feeding cost via a small-bore tube with elemental diet exceeded that of PEG by more than tenfold. This author’s experience with these 26 patients has led to the conclusion that PEG is safe, easy to perform, and effective means of creating feeding gastrostomy without laparotomy or general anesthesia. The authors suggest that PEG be the preferred route of alimentation in those patients who are unable to swallow for prolonged periods of time.

Morphological change in pancreatic islets, insulin binding and intracellular glucose metabolism in adipocytes of streptozotocin-induced diabetic rats

To examine the diabetogenic mechanism of streptozotocin, a histological study was performed on the pancreatic islets of male Wistar rats 7 days after an intravenous injection of streptozotocin (75 mg/kg). Furthermore, for the investigation into mechanism of insulin resistance in the insulin-dependent diabetic rats, insulin binding, glucose transport, and lipogenesis were studied in the isolated adipocytes of streptozotocin-induced diabetic rats. 1) The rate of weight gain in the control rats and the diabetic rats were 2.2 ± 1.8 g/day and −2.4 ± 2.1 g/day, respectively (p<0.05). The serum insulin levels in the control rats and the diabetic rats were 23.1 ± 10.8 μU/ml and 16.9 ± 10.6 μU/ml respectively (p<0.05). The plasma glucagon levels in the control rats and the diabetic rats were 165.7 ± 124.9 pg/ml. and 151.2 ± 78.2 pg/ml, respectively (p>0.1). 2) Microscopic examination of the pancreatic islets of the diabetic rats revealed a severe degranulation and disintegration of B cells. Electron microscopic examination showed a disruption of the intracytoplasmic organelles of B cells with complete degranulation. But the morphology of A cells was normal. 3) Maximal specific insulin binding to receptors in the adipocytes of the diabetic rats (2.10 ± 0.30%) showed an increase compared with that of the control rats (1.12 ± 0.21 %) (p<0.05). 4) Insulin receptor concentration in the adipocytes of the diabetic rats (2.33 ± 0.43 ng/0.5 × 10⁵ cells) also showed an increase compared with that of control rats (1.03 ± 0.15 ng/0.5 × 10⁵ cells) (p<0.05). 5) The average affinities in the adipocytes of the diabetic rats slightly decreased in the low receptor occupancy state compared with that of the control rats. 6) Basal and insulin-stimulated glucose transports in adipocytes of the diabetic rats decreased compared with that of the control rats. The maximal glucose transport in the adipocytes of the diabetic rats was 31.7% of the control value (p<0.005). 7) Basal and insulin-stimulated lipogenesis in adipocytes of the diabetic rats decreased compared with that of the control rats. The maximal lipogenesis in the adipocytes of the diabetic rats was 38.4% of the control value (p<0.005). It can be concluded that streptozotocin produces a diabetogenic mechanism in Wistar rats by directly injuring the pancreatic B cells and inducing hypoinsulinemia. The insulin resistance in the streptozotocin-induced diabetic rats results from the defects in the intracellular glucose metabolism such as glucose transport and lipogenesis.

Multiple myeloma in Korea--clinical analysis and treatment results in 61 cases

A clinical analysis was made of 61 cases of multiple myeloma diagnosed between January 1976 and June 1984 at Seoul National University Hospital using the criteria of the Southwest Oncology Group.

The following observations were made. 1) The major clinical problems at Initial presentation were bone pain(52%), anemia(20 %), renal impairment(11%), and infection(10%). 2) Clinical stages at presentation were stage I, 11%; stage II, 8%; and stage III, 81% of patients. Three(5%) of the patients in stage II and 18(31%) in stage III showed renal impairment with a serum creatinine ≥2.0 mg/dl. 3) Combination chemotherapy produced a response rate of 29% with melphalan and prednisone, and 40% with M2 protocol(among 14 and 20 evaluable patients respectively). Both regimens showed statistically significant survival difference between responders and non-responders(p <0.01). 4) The median survival of all patients was 13 months. 5)Age, calcium level, creatinine level, and performance status were important prognostic factors on survival.

Renal and renin effects of sodium thiopental in rabbits

Unilateral renal arterial infusion of sodium thiopental on renal function and renin secretion were investigated in unanesthetized rabbits. Sodium thiopental infusion in doses of less than 0.3 mg/kg/min into unilateral renal artery caused dose-dependent increases in urine flow, urinary excretion of electrolytes, fractional excretion of sodium and free water clearance with no changes in systemic blood pressure and clearance of p-aminohippuric acid (renal blood flow). An anesthetic dose of sodium thiopental administered intravenously caused decreases in systemic blood pressure, renal hemodynamics, urine flow and free water clearance during the early period of anesthesia followed by increases in urinary excretion of sodium and fractional excretion of sodium. Unilateral renal arterial infusion of sodium thiopental decreased the renin secretion rate and plasma norepinephrine concentration in renal vein, whereas an anesthetic dose of sodium thiopental administered intravenously increased the renin secretion rate. These observations suggest that the diuretic, natriuretic and renin suppressive effects of sodium thiopental may be due to an inhibition of intrarenal sympathetic nervous system or due to a direct tubular action.

Complex chromosomal abnormalities in a patient with lymphoid blast crisis of chronic myelogenous leukemia

A 46-year-old Chinese man underwent lymphoid blast crisis (Ia+, CALLA+, TdT+) after 5 years of chronic phase, Philadelphia-chromosome positive chronic myelogenous leukemia. Chromosome analysis revealed a hyperdiploid karyotype, including two Philadelphia chromosomes--55,XY,t(9;22) (q34;q11), +2, +5, +5, +6, +10, +18, +19, +21, +del(22)(qll----qter)--in the majority of the leukemic blasts. The constellation of a lymphoid blast crisis and complex chromosomal abnormalities usually associated with myeloid blast crisis as well as the clinical data are discussed.

Erythrocyte Na(+)-K+ ATPase activity in the genesis of reducing renal mass in hypertensive rats

To study the relationship between natriuretic factor and experimental low renin hypertension, the erythrocyte Na⁺-K⁺ ATPase activities in the genesis of reducing renal mass in hypertensive rats were measured. The results were as follows : 1. The fractional excretion of Na in hypertensive, reduced renal mass rats (saline-drinking) was higher than that of normotensive, reduced renal mass rats (water-drinking) (p<.001). The plasma renin activities in the hypertensive group were markedly lower than those of the normotensive group (p<.001). 2. The total ATPase activities of rat erythrocyte membrane in the hypertensive group were lower than in those of the normal and the normotensive groups (p<.001, p<.02). 3. The Mg⁺⁺-ATPase activities of rat erythrocyte membrane in the normotensive group tended to decrease significantly (p<.001), but the differences between the normotensive and hypertensive group were not significant. 4. The Na⁺-K⁺ ATPase activities of rat erythrocyte membrane in the hypertensive group were lower than those of the normal and the normotensive group (p<.001). However, the difference between the normal and the normotensive groups was not significant. 5. When erythrocyte membrane taken from normal rats was incubated with supernates of boiled plasma from normotensive rats, the total ATPase activities of erythrocyte membrane were not different from those of hypertensive rats. 6. When erythrocyte membrane taken from normal rats was incubated with supernates of boiled plasma from normotensive rats, the Mg⁺⁺ ATPase activities of erythrocyte membrane were lower than those of hypertensive rats (p<.01). 7. When erythrocyte membrane taken from normal rats was incubated with supernates of boiled plasma from hypertensive rats, the Na⁺-K⁺ ATPase activities of erythrocyte membrane were lower than those of normotensive rats (p<.01). Based on the above findings, it is suggested that the pathogenesis of low renin, reduced renal mass hypertension is primarily mediated by a natriuretic factor (or an ouabain-like factor, inhibitor of Na⁺-K⁺ ATPase) produced by extracellular fluid volume expansion.

Prenatal diagnosis of a de novo complex chromosomal rearrangement involving four chromosomes

A complex chromosome rearrangement, apparently a balanced translocation involving chromosomes 4, 6, 15 and 16, was found in cultured cells of amniotic fluid from a 32-year-old primigravida who requested amniocentesis for prenatal diagnosis because of a family history of mental retardation. Chromosome analysis of peripheral blood from both parents were normal. The couple was counselled for the prenatal diagnosis of this de novo complex translocation and, subsequently, elected to terminate the pregnancy. Post-mortem examination revealed a 23-week fetus with intrauterine growth retardation. The identical chromosome rearrangement was subsequently confirmed in cultured fibroblasts from skin and cord obtained from the abortus. To our knowledge, this is the first report where routine prenatal diagnosis revealed a fetus with a balanced complex chromosomal rearrangement involving four chromosomes of de novo origin.

Prenatal diagnosis of dyssegmental dwarfism

Fetal ultrasound evaluations at 18 weeks gestation on two consecutive pregnancies of a woman who previously gave birth to a stillborn female affected with dyssegmental dwarfism, resulted in accurate diagnoses of unaffected and affected fetuses. Marked disorganization of vertebral bodies and associated encephalocele found in two affected cases in this family are consistent with the original observation of this new syndrome as two major aspects which differentiate it from other forms of lethal dwarfism.

Acute nonlymphocytic leukemia following gastric adenocarcinoma treated by surgery alone. Evidence for etiologic heterogeneity of "secondary" leukemias

The case of a 36-year-old Hispanic man who developed acute nonlymphocytic leukemia 18 months following gastric adenocarcinoma treated by surgery alone is presented. Cytogenetic analysis of the leukemic cells revealed numerical and structural chromosomal rearrangements including chromosomes 5 and 7 and immunologic characterization of the blasts revealed terminal deoxynucleotidyltransferase positivity with monocytoid features. This report suggests that not all cases of acute nonlymphocytic leukemia following chemotherapy and/or radiotherapy, which characteristically display similar cytogenetic and immunologic features, should be exclusively ascribed to the leukemogenic properties of anticancer treatment.

Philadelphia-chromosome-negative chronic myelogenous leukemia with incomplete trisomy 1q following chemotherapy for ovarian carcinoma

A 59-year-old woman was treated with surgery followed by monthly injections of the alkylating agent thiotepa for a granulosa cell tumor of the left ovary. Chemotherapy was continued for 22 years. At the age of 84, chronic myelogenous leukemia (CML) developed. Cytogenetic studies revealed incomplete trisomy of the long arm of chromosome No. 1 as the only karyotypic abnormality. No Philadelphia chromosome was detected. The significance of trisomy 1q as an isolated cytogenetic abnormality in CML and the occurrence of CML following treatment of ovarian cancer are discussed.

Binding site specificity of gamma-radiation-induced crosslinking between phenylalanine and a phenylalanine-containing tetrapeptide

The binding site specificity of crosslinking mediated by the hydroxyl radical has been investigated in a simple model system: a tetrapeptide, Gly-Gly-Phe-Leu, and 14C-labeled phenylalanine. Crosslinking leads to the tetrapeptide-phenylalanine adduct which has been isolated by gel filtration. The amino acid analysis of these adducts compared with those of gamma-radiation-induced dimers of the tetrapeptide and of the dipeptide, Gly-Phe, shows that only the phenylalanine residue is affected and that the same new peaks appear in each case. Spectrophotometric measurement indicates that the extinction coefficient at 260 nm of dimeric tetrapeptide is four times higher than that of monomeric, as is dimeric phenylalanine compared to monomeric. These observations suggest a common crosslinking mechanism in all three cases that involves the aromatic ring of phenylalanine. The appearance of several radioactive peaks in the gel filtration separation of the acid hydrolysate of the adduct suggests that the crosslinking involves more than one possible modification of the phenylalanine. Three distinct tetrapeptide-Phe species, corresponding to molecular weights of 555, 573, and 591, were observed by fast atom bombardment mass spectrometry. The partial release of radioactive phenylalanine from the tetrapeptide-phenylalanine adducts by acid hydrolysis indicates the liability of some phenylalanine-phenylalanine bonds.

Binding-site specificity of the radiolytically induced crosslinking of phenylalanine to glucagon

The gamma-radiation-induced crosslinking of phenylalanine to glucagon, mediated by OH ., has been shown to involve a limited number of binding sites on the glucagon molecule. Glucagon-phenylalanine adducts were partially separated from other radiolysis products with Sephadex gel filtration; further isolation of adducts was achieved with reverse-phase high-performance liquid chromatography (HPLC). Amino acid analysis of the isolated adducts indicates that the aromatic residues (phenylalanine and tyrosine), basic residues (histidine and lysine), and sulfur-containing residue (methionine) of glucagon are predominantly involved in crosslinking; these are essentially the same residues implicated in glucagon-glucagon crosslinking. Acid hydrolysates and chymotryptic digests of glucagon-phenylalanine adducts were examined with HPLC. The number of amino acid-phenylalanine adducts and also chymotryptic peptides observed was much greater than would have been expected based on the amino acid analysis. This observation is best accounted for by the involvement in crosslinking of radicals formed on the glucagon with more than one possible phenylalanine-derived free radical.

Gamma-radiation-induced interactions between amino acids and glucagon

The interaction of glucagon and phenylalanine mediated by the OH . radical causes formation of higher molecular weight products of glucagon and phenylalanine, loss of amino acid residues in glucagon, and formation of adducts of glucagon and phenylalanine. The relative yields of these products depend upon the molar ratio of phenylalanine to glucagon in solution. At low ratios, glucagon aggregation and loss of amino acid residues predominate; at high ratios, the formation of phenylalanine dimers (and possible trimers and tetramers) predominates. The formation of adducts reaches a maximum at a phenylalanine:glucagon molar ratio of 3-4, and then decreases gradually, as the molar ratio increases, but is still discernible even at high molar ratios. Mechanisms for the formation of adducts are suggested. The influence of the primary aqueous radical intermediates, OH., H., and e-aq, on adduct formation has been evaluated for several different amino acids by irradiating in the presence of specific radical scavengers. For the aromatic amino acids (phenylalanine, tryptophan, and tyrosine), OH. is considerably more effective than e-aq for mediating adduct formation, whereas for histidine and methionine, these primary radicals are equally effective.

Tn10 transposase acts preferentially on nearby transposon ends in vivo

Transposition of Tn10 requires sites at the termini of the element and one essential transposon-encoded function, "transposase", which acts at those termini. Genetic complementation experiments reveal that this "transposase" function works much more efficiently on transposon ends located near the gene from which they are expressed than on transposon ends located at a distance. This property accounts for the failure of mutant Tn10 elements to be efficiently complemented in trans. The failure of transposase protein to move freely in three dimensions could be explained by one-dimensional diffusion, energy-dependent translocation and/or extreme protein lability. Additional genetic analyses demonstrate that the rate of Tn10 transposition in vivo depends upon the length of the transposon and the amount of transposase protein. Function dependence and length dependence are independent aspects of the transposition process that could correspond to the break/join and replication aspects into which transposition has been separated conceptually.

Metabolic response to starvation. I. Relative effects of pregnancy and sex steroid administration in the rat

Increased sensitivity to a fast with rapid onset of ketosis, hypoalaninemia, and hypoglycemia is characteristic of rat and human gestation. The present study examines the role of sex steroids in the development of these metabolic changes. Subgroups of female rate received 10 microgram of estradiol (E), 10 mg of progesterone (P), or the two in combination (E + P) s.c. daily for 5 days. Control rats (C) received sesame oil alone. Different groups were starved 12, 24 and 48 hr during days 4 and 5 or treatment. Plasma substrate and insulin responses were measured and compared to results of similar studies performed on rats in late gestation. Administration of E or P along had no significant effects on measured parameters as compared to control values. However, the combined E + P regimen resulted in significantly higher ketonemia, greater hypoalaninemia, and relatively higher triglyceride concentrations than in control groups during fasting. Plasma triglyceride, free fatty acid, and ketone concentrations in the pregnant group exceeded values of both the E + P and control animals. However, plasma free fatty acids in the E + P group were significantly lower as compared to control values during starvation. These data suggest that the combined effects of estradiol and progesterone enhance ketogenesis and hypoalaninemia independent of the fetal-placental unit during starvation in pregnancy. Since the ketogenic effect was associated with a relative suppression of plasma free fatty acids, this may be indicative of a direct action of these hormones on hepatic disposition of free fatty acids and/or the biosynthetic pathways for ketone body production.

Metabolic response to starvation. II. Effects of sex steroid administration to pre- and postmenopausal women

Premenopausal women become more ketotic than do men during short term starvation. The possible influence of female sex steroids on ketosis during an 84-hr fast was studied in premenopausal women receiving combined oral contraceptive steroids. The results were compared to age and weight-matched women on no steroid birth control regimen. Although concentrations of several plasma substrates, insulin, and glucagon were measured throughout the fast, no differences between groups were observed with the exception of the 36-hr interval. At this time total plasma ketones and betahydroxybutyrate were significantly higher in women receiving oral contraceptives. In a second study six postmenopausal women were investigated in a similar fashion during a 36-hr fast. The procedure was repeated following a 5 day treatment regimen of oral estradiol and medroxyprogesterone acetate. After sex steroid treatment, total plasma ketones and betahydroxybutyrate concentrations exceeded control values significantly at 36 hr while plasma alanine and free fatty acid levels were significantly lower. The results suggest that oral estrogen-progestin combinations increase the ketogenic response of pre- and postmenopausal women during the early phases of total starvation. This hormonal effect may explain, in part, why women are more sensitive to fasting than are men.

Chronic mucocutaneous candidiasis with candida granuloma treated with 5-fluorocytosine

A 19-year-old male had chronic mucocutaneous candidiasis with typical granuloma on the face, scalp and genital area. He had defects in cell-mediated immunity (cutaneous anergy to common antigens, but normal number of T lymphocytes and normal lymphocyte transformation with phytohemagglutinin), and there were no endocrine deficiencies. He had systemic involvement, including lungs, kidneys, liver and spleen diagnosed by radiologic studies. In the histologic findings of the skin, typical features were seen of candida granuloma lesions, and hyphae and spores of Candida albicans also were identified in the Malpighian layer. Therapy with 5-fluorocytosine resulted in a remarkable improvement.

Effects of parathyroid hormone infusion and primary hyperparathyroidism on serum prolactin in man

Serum PRL, parathyroid hormone (PTH), and Ca levels were measured in 14 patients (8 women and 6 men) with primary hyperparathyroidism. Six normal volunteers (3 men and 3 women) received a 1-h control infusion of 5% glucose containing 2% human serum albumin, a 1-h infusion of the same fluid containing 450 U bovine PTH, and a repeated 1-h infusion of glucose and albumin. Serum PRL was measured during these infusion periods and showed a peak within 30 min of the start of bovine PTH infusion; PRL levels declined therafter in spite of continued PTH infusion. Serum PRL levels returned to normal within 1 h of discontinuance of bovine PTH infusion. The serum PRL levels in patients with primary hyperparathyroidism were within the normal range, and there was no correlation between serum PTH and PRL levels. These results suggest that the PRL response to PTH infusion is a pharmacological rather than a physiological or pathophysiological effect of PTH.

Correlation of hyperprolactinemia with altered plasma insulin and glucagon: similarity to effects of late human pregnancy

Plasma glucose and insulin concentrations were measured during oral glucose and iv tolbutamide tolerance tests in nine women with hyperprolactinemia and the amenorrheagalactorrhea syndrome (AGS). Glucose tolerance curves, basal insulin levels, and postchallenge plasma insulin responses were significantly higher in AGS women compared to those in an age- and weight-matched control group. Fasting plasma glucagon concentrations were unaltered in AGS, but suppression of the hormone after oral glucose was greater and more prolonged relative to the control response. Oral glucose tolerance tests were performed on nine normal women during late pregnancy who had physiological hyperprolactinemia comparable to that in the AGS group. Glucose tolerance curves, exaggerated plasma insulin responses, and glucagon suppression resembled those observed in the AGS women. These results suggest that elevated plasma PRL concentrations may contribute to the development of hyperinsulinemia and accentuated glucagon suppression in response to glucose that is characteristic of late human pregnancy.

Studies of murine complement. Correlation of hypocomplementemia with other disease parameters in individual NZB/W mice and demonstration of anti-complementary material

We have utilized a new assay for murine complement components to explore the relationship of complement titers to other parameters of disease activity in individual NZB/W female mice. Titers had fallen significantly by 6 months of age, concomitantly with the appearance of antiDNA in serum and of C3 and immunoglobulin in renal glomeruli. The period of hypocomplementemia antedating proteinuria was extremely variable. Heat stable anti-complementary material was found in serum from older NZB/W mice.

Clinical significance of synovial fluid total hemolytic complement activity

Total hemolytic complement (CH50) was measured in 174 synovial fluids (SF) to determine its diagnostic and and prognostic value. SF CH50 was reduced relative to serum CH50 in 61% of patients with rheumatoid arthritis and 60% of patients with crystal-induced arthritis. There was no correlation of SF CH50 levels with disease duration, SF leukocyte count, presence of IgM rheumatoid factor, or radiologic evidence of erosions.

Cryptococcosis with cutaneous manifestations treated with 5-fluorocytosine

A 3-year-old girl in poor general condition was admitted with a diagnosis of cryptococcosis and treated with 5-fluorocytosine. This case is characterized by its occurrence at a young age with no underlying disease, with involvement of the central nervous system, lung, skin, liver, spleen and lymph nodes, with typical cutaneous papules and nodules with ulceration and crushing, gelatinous appearance on biopsy of the skin, severe peripheral eosinophilia, and a remarkable response to 5-fluorocytosine therapy monitored by follow-up skin biopsies.

Changes in lipoprotein composition during the menstrual cycle

Composition of major plasma lipoproteins was studied in 14 normal women during different phases of the menstrual cycle for three consecutive months. The results were compared to measurements in ten normal age-matched men for a comparable period, to delineate possible sex differences in lipoprotein metabolism in young adults. Blood samples were obtained every 3--5 days after a 14-hr overnight fast and processed for determinations of total plasma cholesterol, LDL- and HDL-cholesterol, and apoproteins B and A-1. In premenopausal women, a significant, 10%--25% cyclical suppression of total plasma cholesterol, LDL-Chol, and LDL-apoB occurred during the luteal phase, which was significantly lower than unchanging concentrations found in men at any time interval. HDL-Chol remained in a significantly higher fixed concentration range in the female subjects as compared to the men. These sex differences in lipoprotein metabolism may have relevance to the reduced susceptibility of premenopausal women to atherosclerosis.