Regulation of lymphocyte blastogenesis and antibody production by soluble factor released by a human B-lymphoblastoid cell line

Yam 1B, a human B lymphoblastoid cell line, spontaneously produced an immunoregulatory factor, which suppresses blastogenesis and antibody formation by human lymphocytes. The Yam 1B cells, which were derived from the peripheral blood of an adult T-cell leukemia patient, have been established and maintained in our laboratory since 1985. This cell line expressed mature B-cell surface antigens including surface immunoglobulin M (IgM), CD23, and HLA-DR; had cytoplasmic IgM; and secreted small amounts of IgM in the culture supernatants. Yam 1B was positive for Epstein-Barr virus-associated antigen (EBNA) but negative for adult T-cell-associated antigen (ATLA). The serum-free Yam 1B culture supernatants (SN) inhibited the expression of transferrin R, but neither the expression of interleukin 2 (IL-2) R(CD25) nor the production of IL-2 in the lymphocytes stimulated with phytohemagglutin. Yam 1B SN also inhibited DNA synthesis by human T and B lymphocytes and immunoglobulin generation by normal B cells as well as by Epstein-Barr virus-transformed human B lymphoblastoid cell lines. The inhibitory activity of Yam 1B SN was inactivated at 56 degrees C and at pH 10 but was relatively stable at pH 2. It was abrogated by digestion with pronase and was partially stable by digestion with trypsin. Fractions collected from a Sephacryl S-300 gel filtration column (Pharmacia Fine Chemicals, Uppsala, Sweden) were found to have a peak of inhibitory activity of cell proliferation associated with molecules of apparent MWr of 43,000 to 67,000. The inhibitory activity of Yam 1B SN was not blocked by the anti-transforming growth factor beta antibody.(ABSTRACT TRUNCATED AT 250 WORDS)

The role of CD45RA on human B-cell function: anti-CD45RA antibody (anti-2H4) inhibits the activation of resting B cells and antibody production of activated B cells independently in humans

Anti-CD45RA antibody defined by anti-2H4 monoclonal antibody has been reported to split CD4+T cells into two distinct subpopulations. CD45RA antigen is present on the surface of virtually more than 95% B lymphocytes in the purified tonsillar B-cell preparations. We examined the role of CD45RA antigen on human B-cell function using this antibody. The addition to anti-2H4 to tonsillar B cells inhibited the proliferative response induced by Staphylococcus aureus Cowan strain I(SAC) in a dose-dependent manner. Kinetic analysis indicated that anti-2H4 exerted its inhibitory effect when added within the first 24 h of culture initiation during a 72-h culture period. Anti-2H4 inhibited the transferrin receptor expression without interfering with the expression of the IL-2 receptor on SAC-stimulated B cells in a short-term culture. Anti-2H4 blocked the progress of SAC-stimulated B cells from the G1 to S phase of the cell cycle. These events suggested that anti-CD45RA MoAb inhibited the proliferative response by directly acting on B cells in the G1 phase. In addition, anti-CD45RA antibody also had a suppressive effect on early phase of B-cell differentiation. This effect appeared to be independent of its suppressive effect on proliferation, because anti-CD45RA did not inhibit the proliferative response of preactivated B cells with lymphokines. These studies suggested that the restricted epitope recognized by anti-2H4 antibody may be directly involved in regulatory function on B cells.

Effects of chronic bromocriptine-induced hypoprolactinemia on plasma testosterone responses to human chorionic gonadotropin stimulation in normal men

To study the role played by normal levels of plasma prolactin (PRL) in the secretion of testosterone (T) in the testes, we induced hypoprolactinemia with a daily dose of 5 mg bromocriptine administered orally in five normal men 20 to 35 years of age for 8 weeks. The basal PRL, T, luteinizing hormone, follicle-stimulating hormone, and maximum responses of plasma T to human chorionic gonadotropin (hCG) stimulation were measured every 2 weeks. Basal levels of plasma T were reduced in the 1st 2-week-long period of hypoprolactinemia. In the 4-week-long period of hypoprolactinemia, the maximal response of plasma T to hCG stimulation was significantly reduced. The findings suggest that normal levels of plasma PRL may play an important role in the secretion of T in the human testes in vivo.

Establishment of a novel cell line with T-lineage phenotype (HPB-MLp-W) from a non-Hodgkin's lymphoma patient

We report the characterization of a novel human T-cell line, HPB-MLp-W, which was established from blastic cells of a lymph node specimen from a patient with non-Hodgkin's lymphoma. They demonstrated the T-cell association antigens, CD2 and CD4, but no CD3, CD8, CD1, CD5, CD7 nor T-cell antigen receptor on their cell surfaces. They were also positive for Ia and Ki-1 antigen, and negative for CD25 (Tac-1). The cell line HPB-MLp-W had the same pattern of antigen expression as the patient's cells. Southern-blot analysis of DNA showed a rearrangement of the T-cell receptor-alpha and beta genes. To our knowledge, this is a novel cell line with unique T-lineage marker, to be established from a case of non-Hodgkin's lymphoma.

Functional analysis of clonally expanded CD8, TCR gamma delta T cells in a patient with chronic T-gamma lymphoproliferative disease

Leukemic cells from a patient with T-gamma lymphocytosis were found to have the surface phenotype, CD3+, CD4-, CD8+, Leu19+, TCR delta 1+, WT31-. The clonal nature of the TCR gamma delta T cell proliferation was documented by flow cytometry and Southern blot analysis. Morphologically, they were large to medium-sized mature lymphocytes with cytoplasmic granules. Functionally, the cells revealed strong cytotoxic activities against NK-sensitive target cells, but had neither killer T cell activity nor suppressive activity on PWM-driven immunoglobulin synthesis by B cells. Interestingly, both suppressive and cytotoxic T cell activities were recovered with the depletion of CD8+ T cells. These studies may suggest some functions of the CD8+ population of human TCR gamma delta T cells in a normal immune system.

High cytotoxic cell activity in the marrow from patients with aplastic anemia

The mechanism which produces marrow failure in idiopathic aplastic anemia is still unknown. Recent investigations have suggested the crucial role of NK cells in the regulation of normal hematopoiesis. In this study, the cytotoxic activity of mononuclear cells from human bone marrow and peripheral blood was examined against three NK-sensitive target cell lines in 15 patients with aplastic anemia as well as 21 normal subjects. Marrow mononuclear cells from aplastic anemia demonstrated a high cytotoxicity comparable to peripheral blood NK cells to these target cells. Neither large granular lymphocytes nor the cells expressing known NK cell surface phenotypes increased in aplastic marrow cell elements. The aplastic marrow cells showed strong killing activity rather than binding at single cell assay. They consisted of non-adherent and adherent cell population in plastic adherence and were unresponsive to IFN treatment. The existence of cytotoxic cells with high NK-like activity may be responsible for the mechanism of marrow failure in aplastic anemia.

Natural killer (NK) cell activity in patients with various malignancy against a variety of target cell lines: re-evaluation of clinical significance of natural killer cell activity

Sixty-eight patients with various malignancy was examined for their natural killer (NK) cell activity against 14 target cell lines. The group consisted of 10 patients with gastric cancer, 10 patients with lung cancer, 8 patients with hepatoma, 11 patients with cancer of female genital organs, 14 patients with malignant lymphoma and 15 patients with acute myelogenous leukemia (AML). The target cells from a variety of lineage were selected to examine the disease-related specificity in NK cell activity. The peripheral mononuclear cells from patients with gastric cancer did not show a decrease in NK activity against 14 targets including gastric cancer cell lines. Other patients except for AML demonstrated low NK activity against one or two target cells out of 14 targets. Whereas, NK activity in patients with AML was remarkably depressed against 10 target cells out of 14. At single cell assay, killing ability rather than binding activity to target was markedly impaired in AML. Comprehensively, the data demonstrated the marked difference in the NK level between the patients with solid tumor and the patients with hematopoietic malignancy. There existed neither disease-related specificity in NK cytolysis, nor correlation in NK levels and clinical severity in the patients with malignancy. These results suggested that it was very difficult to evaluate the anti-cancer capacity in patients with malignancy by NK activity alone.

Depressed natural killer (NK) function in blood and marrow is related to the decrease in CD 11+ cells in acute leukemia

The natural killer (NK) cell activity of the blood and marrow was studied in patients with acute myelogenous leukemia (AML). NK activity of the cells from blood and marrow was significantly decreased in AML to three target cell lines. Both binding and killing capacities of the effector cells were deeply depressed in the blood as well as in the marrow at single cell assay. Surface phenotypic analysis showed a significant decrease in CD 11+ cell subsets, but not in CD 16+ or Leu-7+ cells, in both blood and marrow cells from AML. A significant decrease of large granular lymphocytes (LGL) was also displayed in these samples at morphological examination. The effector cells from AML patients poorly responded to interferon stimulation in NK cytolysis. Taken together, a decrease in CD 11+ cell population with LGL morphology appeared to be responsible for the impaired NK activity in patients with AML.

Enhanced natural killer cell activity in patients with pulmonary tuberculosis

The natural killer (NK) cell activity of patients with pulmonary tuberculosis (TB) was studied using blood samples. The patients with pulmonary TB showed higher NK activity to 10 out of 12 NK-sensitive target cell lines than healthy subjects did. When NK activity was compared between active and inactive stages of the disease, the patients with active TB demonstrated higher NK activity than did patients with inactive TB. Furthermore, active patient displayed cytolysis to one out of 4 NK-resistant target cell lines. In study of NK cell cyotoxicity at single cell level, higher killing activity than binding activity to target cells was observed in patients at an active stage. Morphological and surface marker analysis of peripheral mononuclear cells showed an increase in CD16+ cells in patients with pulmonary TB. These results suggested that NK cell activity is augmented qualitatively and quantitatively in patients with pulmonary TB.

Bestatin, an inhibitor of aminopeptidase B, suppresses the proliferation and differentiation of human B-cells in vitro

Bestatin, an inhibitor of aminopeptidase B, was examined for its effect on B-cell activation. Small, dense B-cells from human tonsil samples were isolated by Percoll density gradients from non-rosetted (E-) cells and were used as target cells. Although bestatin was not cytotoxic towards B-cells, it inhibited the proliferative response of B-cells induced by SAC- or PMA-stimulation. The inhibition of cell proliferation by bestatin was manifested as cell arrest caused by the selective block of G1b to S phase transition. This inhibitory effect was prevented by the addition of B-cell growth factor (BCGF) or interleukin-2 (IL-2). The presence of BCGF or IL-2 at the initiation of the culture prevented the bestatin-mediated suppressive effect on B-cell proliferation. Bestatin also has a direct inhibitory effect on the differentiation of B-cells independent of its suppressive effect on B-cell proliferation, which was not relieved by T-cell help. Conversely, bestatin suppressed neither proliferation nor Ig secretion of human B lymphoblastoid cell lines, although aminopeptidase activities on the membrane of these cell lines were strongly inhibited by bestatin. These results indicated that bestatin selectively suppressed normal B-cell proliferation and differentiation. Although several studies have demonstrated that bestatin has immunopotentiating effects in tumor-bearing subjects, the above results indicated that the mechanism of immunopotentiation by bestatin is not a direct stimulatory effect on B-cells.

Effects of chronic sulpiride-induced hyperprolactinemia on menstrual cycles of normal women

We investigated the influence of chronic (27-65 days) sulpiride-induced hyperprolactinemia on the menstrual cycles of four normal women. The hyperprolactinemia (206.4 ng/mL, the average of the mean values of each subject obtained by sulpiride treatment) suppressed the LH surge and the secretion of plasma estradiol-17 beta and progesterone to their basal levels. The results suggest that the endocrine changes in normal women with sulpiride-induced hyperprolactinemia are similar to those in women with spontaneous hyperprolactinemia. Sulpiride-induced hyperprolactinemia may be useful as a model for studying spontaneous hyperprolactinemia.

Effects of chronic sulpiride-induced hyperprolactinemia on plasma testosterone and its responses to hCG in normal men

To elucidate the effects of sulpiride-induced (300 mg daily) long-term (64 days) hyperprolactinemia on basal and hCG-stimulated plasma testosterone (T), hCG was given to five normal men five times at 2-week intervals (before sulpiride administration and at 2, 4, 6 and 8 weeks). Mean integrated hCG responses of plasma T did not change significantly as compared with baseline. However, mean (+/- SEM) basal plasma levels of T decreased significantly (P less than 0.05) from 1011 +/- 148 ng/dl to 852 +/- 13 at 2 weeks, 520 +/- 53 at 4 weeks, 572 +/- 137 at 6 weeks and 554 +/- 140 at 8 weeks. These results suggest that sulpiride-induced hyperprolactinemia (73.8 ng/ml, the average of mean values obtained at 2, 4, 6 and 8 weeks) for 64 days does not suppress secretion of T in response to hCG in spite of a decrease in basal plasma T concentrations. It is unlikely that the low concentrations of plasma T are due to direct effects of hyperprolactinemia on the testis.

Parathyroid hormone-induced lipolysis in human adipose tissue

Relative lipolytic activity of human parathyroid hormone-(1-34) (hPTH-(1-34], hPTH-(3-34), desamino-Ser1-hPTH-(1-34), and rat PTH-(1-34) was compared in human subcutaneous adipose tissues in vitro. Human PTH-(1-34), rat PTH-(1-34), and desamino-Ser1-hPTH-(1-34) stimulated in vitro lipolysis significantly above basal level at the concentration of 10(-6) M. Average increments of lipolytic rate were 2.39, 1.82, and 0.87 mumol/g per 2 hr, respectively, being significantly different among the three groups. On the other hand, hPTH-(3-34)-induced lipolytic rate was 0.83 +/- 0.18 mumol/g per 2 hr, not significantly different from the basal level (0.71 +/- 0.20 mumol/g per 2 hr). The effect of hPTH-(3-34) on glycerol release stimulated by hPTH-(1-34), isoproterenol, or forskolin was subsequently investigated. Human PTH-(3-34) produced a dose-dependent inhibition of hPTH-(1-34)-stimulated lipolysis. In contrast, isoproterenol- and forskolin-induced lipolytic rates were not influenced by hPTH-(3-34). The effect of propranolol on hPTH-(1-34)- or isoproterenol-induced lipolysis was also studied. Propranolol dose-dependently inhibited isoproterenol-induced lipolysis but had no effect on lipolysis stimulated by hPTH-(1-34). These results suggest that the amino acids at positions 1 (serine) and 2 (valine) of PTH are critical for the stimulation of lipolysis in human adipose tissue. Human PTH-(1-34) causes lipolysis after binding to receptors distinct from beta-adrenergic receptors of fat cells and possibly hPTH-(3-34) inhibits hPTH-(1-34)-stimulated lipolysis by competing at the level of PTH receptor.

No substrate specificity of converting enzyme for N-terminal substituted angiotensin I in man

In 5 normal men sarcosine1-angiotensin II (Sar1-ANG II) (Exp. 1) and sarcosine1-angiotensin I (Sar1-ANG I) (Exp. 2) infused iv at a rate of 5 pmol/kg X min from 0900 h to 0930 h caused the same degree of rise in blood pressure (BP). But 100 mg of captopril given orally at 0800 h (Exp. 3) completely abolished the BP rise by Sar1-ANG I. In Exps. 1 and 2 plasma renin activity (PRA) decreased and plasma aldosterone (PA) increased after the infusions. In Exp. 3 PRA increased markedly and PA decreased 60 min after captopril, and at 30 min of Sar1-ANG I infusion PRA decreased to the pre-captopril level despite no BP change but PA was kept at the pre-infusion level. Hence, substrate specificity of converting enzyme previously demonstrated for N-terminal deleted ANG I was not shown for N-terminal substituted ANG I in man because the conversion of Sar1-ANG I to Sar1-ANG II was 100%. Sar1-ANG I may possibly inhibit renin release in normal men.

Biological activities of sarcosine1-angiotensin I in man

In order to examine whether substrate specificity of angiotensin-converting enzyme (ACE) exists or not for N-terminal substituted angiotensin I (ANG I) in man, biological activities of sarcosine1-angiotensin I (Sar1-ANG I) and the effects of an ACE inhibitor, captopril, on the Sar1-ANG I activities were studied in 5 normal men. The following 3 experiments were done at 1 week intervals. Sarcosine1-angiotensin II (Sar1-ANG II) was infused iv at a rate of 5 pmol/kg X min from 0900 h to 0930 h in 5 normal men in a recumbent position. Blood pressure rose remarkably and the average increment was 38/31 mmHg at 30 min (p less than 0.001). Average duration of the pressor action after the cessation of the infusion (T) was 40 min for systolic and 50 min for diastolic and much longer than T of isoleucine5-angiotensin II. Plasma renin activity (PRA) decreased (p less than 0.01) and plasma aldosterone (PA) increased significantly (p less than 0.01). Sar1-ANG I was infused iv at a rate of 5 pmol/kg X min from 0900 h to 0930 h. Blood pressure rose to the same extent as in (1) (p less than 0.001). T was 40 min for both systolic and diastolic and much longer than T of ANG I in man. PRA decreased (p less than 0.01) and PA increased (p less than 0.01) significantly. Oral 100 mg captopril was given at 08:00 h and Sar1-ANG I was infused iv at a rate of 5 pmol/kg X min from 09:00 h to 09:30 h.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of chronic hyperprolactinemia induced by sulpiride on plasma dehydroepiandrosterone (DHA) in normal men

In order to elucidate the relationship between plasma dehydroepiandrosterone (DHA) and sulpiride-induced hyperprolactinemia (of 60 day duration) in normal men, five normal men (aged 27-46) were administered daily 300 mg of sulpiride orally for 60 days to induce hyperprolactinemia. Plasma levels of prolactin, DHA and cortisol were measured by radioimmunoassay before sulpiride treatment, at day 14 and day 60 after initiation of the treatment. Plasma levels of prolactin after the administration rose significantly (P less than 0.001) to 71.6-95.3 ng/ml in four out of the five subjects compared with those of the controls. In the same four subjects the mean DHA values in plasma were elevated significantly (P less than 0.05) to 877 +/- 160 ng/dl from the mean baseline values (669 +/- 91 ng/dl). The elevated values remained during sulpiride treatment. Plasma levels of cortisol did not change significantly during sulpiride administration in all subjects. Our results suggest that sulpiride-induced hyperprolactinemia sustained at least 14-60 days in normal men stimulates the adrenal cortex to secrete DHA.

Neutral glyceride synthesis from glucose in human adipose tissue: comparison between growing and mature subjects

Basal and insulin-stimulated neutral glyceride syntheses from glucose were studied in fat cells of different size (fat cell volume, 0.07-0.20, 0.20-0.60, 0.60-1.00, 1.00-1.50 micron3 X 10(6)) obtained from subcutaneous adipose tissues in 20 subjects aged 3 months to 67 years. In 0.07-0.20 or 0.20-0.60 micron3 X 10(6) fat cells, the basal rate of glucose conversion to neutral glyceride was significantly lower in mature (36 to 67 years old) than in growing (0 to 12 years old) subjects. In 0.60-1.00 or 1.00-1.50 micron3 X 10(6) fat cells, however, basal rate was not significantly different between the two groups. The stimulating effect of insulin on conversion of glucose to neutral glyceride was not significantly different from the basal rate in fat cells of each size taken from the mature subjects, whereas in fat cells from growing subjects, it was significantly different from the basal rate in each fat cell size category. These results indicate that when fat cell size is taken into account, not only is the rate of basal glucose conversion to neutral glyceride higher in growing subjects but also its responsiveness to exogenous insulin, and that insulin insensitivity of large fat cells, reported previously, may be influenced by age.

Biological activities of angiotensin II-(1-6)-hexapeptide and angiotensin II-(1-7)-heptapeptide in man

Biological activities of angiotensin II-(1-6)-hexapeptide [ANG-(1-6)] and angiotensin II-(1-7)-heptapeptide [ANG-(1-7)] were studied in 5 normal men and 3 patients with Bartter's syndrome. The angiotensins were infused iv in each subject from 0900 h to 0915 h at a rate of 21 nmol(16.8 micrograms)/kg X min and 18 nmol(16.2 micrograms)/kg X min for ANG-(1-6) and ANG-(1-7), respectively. In the normal men a significant rise in blood pressure was observed by the infusions of both peptides. Average increments of blood pressure for ANG-(1-6) were 17/14, 23/18, 22/15 and 17/14 mmHg at 2, 5, 10 and 15 min, respectively, and those for ANG-(1-7) were 19/15, 20/17, 13/13 and 15/13 mmHg at 2, 5, 10 and 15 min, respectively. The duration of pressor actions after the cessation of the infusions (T) was 10 min for ANG-(1-6) and 20 (for systolic) and 30 (for diastolic) min for ANG-(1-7). T for ANG-(1-6) was shorter than and T for ANG-(1-7) was similar to T for Ile5-angiotensin II (Ile5-ANG II) reported previously in 7 normal men 5 of whom were the same as examined in the present study. On the other hand, both peptides did not cause a rise in blood pressure in the 3 patients with Bartter's syndrome. Both angiotensins did not cause an increase in plasma aldosterone but did cause a significant decrease in plasma renin activity both in the normal men and in the patients. From these results and our previous observations of inactivity of angiotensin II-(5-8)-tetrapeptide, a pressor action of angiotensin II-(4-8)-pentapeptide, and pressor, renin-suppressing and steroidogenic actions of angiotensin II-(3-8)-hexapeptide in normal men, it is thought that ANG-(1-6) and ANG-(1-7) are bound to angiotensin II (ANG II) receptor in the peripheral arterioles and show pressor actions (less than 0.024% and less than 0.028% of Ile5-ANG II, respectively) and suppress renin mainly via short loop feedback and that the shortest biologically active ANG II molecules for pressor, renin-suppressing and steroidogenic actions are Tyr-Ile-His, Val-Tyr-Ile-His and Val-Tyr-Ile-His-Pro-Phe, respectively, in man. It is also evident that ANG-(1-6) is more rapidly metabolized than ANG-(1-7) or Ile5-ANG II in man.

Natural killer cell activity against a variety of target cell lines in normal persons: NK-target sensitivity and effect of age and sex on NK levels

Natural killer (NK) cells have been implicated as first line of defence mechanism for carcinogenesis in humans. A lot of studies of depressed NK activity in patients with malignancies have supported this. Two major problems, however, in these studies are the choice of normal controls and target cells. To study this problem, peripheral mononuclear cells (PBMC) of sixty-six normal subjects from young and elderly, males and females were tested for NK function against twenty target cell lines with a microcytotoxicity assay. The result was shown that no sex or age difference existed with respect to NK function, except for a slight but significant decreased in NK activity of young female to K562 target cells. Target cells were divided into four groups by their NK sensitivity, namely, high, moderate, low and refractory sensitive. In general, NK activity of healthy persons is considered to remain stable and polyspecific in our results.

A case of adiposis dolorosa: lipid metabolism and hormone secretion

The present report describes a 53-year-old non-obese man with adiposis dolorosa whose pain was dramatically relieved by the intravenous injection of lidocaine. The patient showed a paradoxical response of growth hormone to thyrotropin-releasing hormone. In addition, in-vitro studies on adipose tissue metabolism revealed the reduced glucose conversion to neutral glycerides in painful adipose tissue. These abnormalities may be related in some ways to the pathogenesis of this disorder.

Pressor activity of angiotensin II-(2-7)-hexapeptide in man

Pressor activity and speed of metabolic degradation of angiotensin II-(2-7)-hexapeptide [ANG-(2-7)] were studied in 5 normal men. When infused iv at a rate of 72 nmol/kg X min for 7 min, ANG-(2-7) caused a very slight but statistically significant increase in blood pressure. Average blood pressure increases at 2, 5 and 7 min were 5/4, 8/10 and 8/9 mmHg, respectively, and the duration of the pressor action after the cessation of the infusion (T) was 5 min on the average. The pressor activity and T of this peptide were much less than or shorter than those of angiotensin II-(1-7)-heptapeptide [ANG-(1-7)] infused previously in the same 5 normal men at a rate of 18 nmol/kg X min, indicating that the pressor activity ratio of both the peptides in man is 1: greater than 7.2 which is similar to that of angiotensin II-(2-8)-heptapeptide (angiotensin III) and Ile5-angiotensin II (Ile5-ANG II) (1: greater than 5) and that the removal of N-terminal aspartic acid from ANG-(1-7) hastens the speed of metabolic degradation of the peptide as from Ile5-ANG II.

Agonistic activities of isoleucine8-angiotensin II in man

In order to clarify the importance of C-terminal phenylalanine in angiotensin II (ANG II) molecule, agonistic activities of a C-terminal substituted peptide, isoleucine8-angiotensin II (Ile8-ANG II), were studied in comparison with those of sarcosine1-, isoleucine8-angiotensin II (Sar1-, Ile8-ANG II) and isoleucine5-angiotensin II (Ile5-ANG II) in 5 normal men. When infused iv at a rate of 600 pmol/kg X min for 30 min, Ile8-ANG II and Sar1-, Ile8-ANG II raised the blood pressure to the same extent (15/15 mmHg on the average), while the average blood pressure increase was 21/21 mmHg after an iv infusion of Ile5-ANG II at a rate of 5 pmol/kg X min for 30 min. Duration of the pressor action after the cessation of each infusion was 50-90, 90-120 and 10-25 min, respectively. In each case plasma renin activity (PRA) decreased and plasma aldosterone (PA) increased. When infused iv at a rate of 10 pmol/kg X min (maximum non-pressor dose) for 120 min, both Ile8-ANG II and Sar1-, Ile8-ANG II lowered PRA and increased PA gradually, but 100 mg oral captopril given immediately before these infusions caused no significant increase in PRA or no significant decrease in PA but again a decrease in PRA and an increase in PA.(ABSTRACT TRUNCATED AT 250 WORDS)