Cimetidine reduces cyclosporine inhibition of interleukin-2 production

Cimetidine has been shown to up-regulate proliferative and cytotoxic immune responses, which are mediated in part by an increase in interleukin-2 (IL-2) production. Cyclosporine achieves its immunosuppressive effect mainly through inhibition of IL-2 production. A recent clinical report of renal allograft recipients with elevated serum creatinine levels while on a histamine type-2 receptor antagonist raised concern whether the cimetidine increase in IL-2 production was counterbalancing the cyclosporine inhibition of IL-2 and thereby increasing alloreactivity to the transplant. We therefore measured IL-2 production of mitogen-stimulated murine spleen cells with or without cimetidine and cyclosporine and in combination of these two drugs. Cimetidine (10(-4) and 10(-5) M) completely reversed the cyclosporine (0.1 ng/ml and 1 ng/ml)-induced 25 and 41% inhibitions of IL-2, respectively. Cyclosporine (10 ng/ml) reduced IL-2 by 64% and cimetidine partially reversed this inhibition to 48%. All cimetidine groups which reduced the cyclosporine effect on IL-2 were statistically significant (P less than 0.05). These data raise concern about the safety of giving histamine type-2 receptor antagonists to allograft recipients without increasing alloreactivity due to a relative increase in IL-2.     

Impaired antibody production in blunt trauma. Possible role for T cell dysfunction

This study investigates mechanisms of impaired humoral immune response in a well-defined population of blunt trauma patients (n = 18, Injury Severity Score greater than or equal to 20). Spontaneous and pokeweed mitogen-induced polyclonal immunoglobulin production were assessed in cultures of peripheral blood mononuclear cells. The proliferative response to alloantigen and mitogen was assessed in parallel by the mixed lymphocyte reaction and pokeweed mitogen-induced blastogenesis, respectively. Pokeweed mitogen-induced IgG and IgM production was significantly reduced in trauma patients compared with controls. This effect was not reversed by depletion of adherent cells or by the addition of indomethacin. Exogenous interleukin 2 was also ineffective. However, the addition of normal T cells or supernatants from isoantigen-stimulated cultures of these cells to patient B cell-enriched cultures significantly enhanced (by 1.4- to 5.1-fold) the antibody response to pokeweed mitogen. Thus, suppression of humoral antibody response in blunt trauma patients may be due to failure of T-cell mediated help, resulting in insufficient secretion or activity of cytokines required for adequate B cell activation, proliferation, or differentiation into immunoglobulin-secreting cells.     

Histamine type-2 receptor antagonist immune modulation. II. Cimetidine and ranitidine increase interleukin-2 production

The effect of cimetidine and ranitidine (histamine type-2 receptor antagonists) on the production of interleukin-2 (IL-2) by mitogen-activated, normal murine spleen cells was studied in vitro. Cimetidine (10(-4) mol/L to 10(-6) mol/L) increased IL-2 production to a maximal 8.8 +/- 1.6 U (IL-2 activity), as compared with media controls of 1 U. Ranitidine (10(-4) mol/L to 10(-6) mol/L) also increased IL-2 production to a maximal 5.6 +/- 1.2 U, as compared with media controls of 1 U. The increases for both drugs were statistically significant- (p at least less than 0.03 for all doses tested). These data suggest that our previously demonstrated immunofacilitation of proliferative and cytotoxic lymphocyte responses by cimetidine was probably mediated by the presence of increased IL-2. These data further suggest that histamine type-2 receptor antagonists may have immunorestorative potential in clinical immunotherapy of IL-2 deficient states.     

Histamine type-2 receptor antagonist immune modulation. I. Increased cell-mediated cytotoxicity in normal and in down-regulated systems

Cimetidine, a histamine type-2 receptor antagonist, is capable of immunoregulating T cell-mediated proliferative responses in both man and mouse. We present data that show that cell-mediated cytotoxicity (CMC) is also increased by cimetidine in normal and down-regulated murine splenocytes. Timed addition and removal of cimetidine from CMC generation cultures localizes the cimetidine effect to the first 24 hours of the alloantigen sensitization process. Cimetidine partially reverses CMC suppression by suppressor cells generated in vitro in a dose response manner; the result depends on the number of suppressor cells added. Mixed tumor lymphocyte cytotoxicity of splenocytes from syngeneic-tumor-bearing mice is increased by in vivo cimetidine treatment, which results in prolongation of concomitant tumor immunity. These data support the concept that cimetidine may have potential as a clinical immunofacilitator in down-regulated states of immunity.     

Modification of lymphocyte responsiveness by hormone used in the treatment of urologic malignancies.

Recognition that the immune system may be important in regulating the clinical evolution of tumors and that corticosteroids suppress immune responses lends relevance to determining the concentrations in which sex hormones, currently used in the treatment of urologic malignancies exert immunosuppressive effects. We have investigated the effects of the sex hormones, diethylstilbestrol, diethylstilbestrol diphosphate, testosterone and progesterone, on in vitro lymphocyte blastogenesis as determined by 3H thymidine incorporation after stimulation with phytomitogens and alloantigens, and compared their effects to the effects of cortisol. Compared to cortisol these sex hormones are relatively weak suppressors of lymphocyte blastogenesis (cortisol 10(-7) M, progesterone 5 times 10(-6) M, testosterone 5 times 10(-5) M, diethylstilbestrol 5 times 10(-5) M and diethylstilbestrol diphosphate 10(-3) M) and probably are not significantly immunosuppressive in commonly used pharmacologic dosages. Similar results were observed with the T lymphocyte mitogens, phytohemagglutinin and concanavalin A, and in the combined T and B cell mitogen pokeweed. The fact that alloantigen-stimulated lymphocyte blastogenesis also was suppressed by diethylstilbestrol indicates that sex hormones exert their effects on the lymphocytes and not on the mitogens. Furthermore, sex hormones were not found to be cytotoxic to lymphocytes. It is postulated that the sex hormones tested act by suboptimal binding to glucocorticoid receptors in the lymphocytes and that the relative immunosuppressive potency of a given hormone is related to its affinity for the glucocorticoid receptor.     

Fluid and mononuclear cells from healing wounds inhibit thymocyte immune responsiveness

It has been shown previously that fluid obtained from 7-day-old wounds noncytotoxically inhibits normal thymic lymphocyte blastogenesis and that mononuclear cells (MNC) from the same wounds lack mitogenic responsiveness. The present series of experiments studies whether wound MNC are the source of the wound inhibitory factor(s) and the effect of adult thymectomy (ATDX) on their generation. Adult male Sprague-Dawley rats (300-350 g), intact or ATDX (performed at 8-10 weeks of age), underwent dorsal wounding (7 cm) and subcutaneous implantation of sterile Ivalon sponges. Seven days later sponges were harvested, wound fluid was obtained, and the cell pellet was purified to 90% MNC. Normal rat thymocyte blastogenesis (stimulation index) to Con A and PHA evaluated in a microculture system (10 separate experiments) was 169.9 +/- 10.0 and 30.1 +/- 3.7. Addition of 10% wound fluid markedly inhibited thymocyte mitogenesis--6.3 +/- 1.0 and 2.7 +/- 0.6, respectively (P less than 0.001). Heat-inactivated wound fluid (56 degrees C, 30 min) had similar inhibitory activity--3.4 +/- 0.9 and 2.7 +/- 0.6 (P less than 0.001). Normal thymic blastogenesis could also be inhibited by the addition of 5 X 10(4) wound MNC to the microculture system--4.4 +/- 1.1 and 1.9 +/- 0.3 (P less than 0.001). Wound fluid from ATDX rats had much less inhibitory activity (77.1 +/- 22.4 and 7.2 +/- 2.1, P less than 0.01) vs control wound fluid. In addition wound MNC from ADTX animals were also less immune suppressive (30.7 +/- 4.9 and 13.5 +/- 3.7, P less than 0.001) than control MNC. Forty-eight-hour supernatants of wound MNC from intact rats, added in 25% concentration to normal thymocyte cultures, demonstrated inhibition similar to that of the wound fluid from the same animals: 4.4 +/- 0.7 and 3.9 +/- 0.6, while ATDX MNC supernatants had minimal inhibitory activity (110.1 +/- 18.2 and 25.7 +/- 6.5, P less than 0.005). No cytotoxicity could be demonstrated in any of these experiments by trypan blue exclusion. It is concluded that 7-day-old wound fluid noncytotoxically inhibits thymocyte blastogenesis; this effect is also demonstrated by wound MNC and their supernatants, suggesting immune "suppressor" lymphocytes are present in wounds; ATDX, which abrogates suppressor cell induction, leads to marked diminution of wound inhibitory activity. The data suggest that important immune events occur at the wound site; their relation to normal wound healing remains to be elucidated.     

Immune responses in the treatment of advanced carcinoma of the breast. Effects of adrenalectomy.

We set out to answer the question, "Is the effect of adrenalectomy associated with or mediated through the immune response?" Eleven patients were studied preoperatively and postoperatively by in vitro immunologic tests. The assay system used included absolute T cell counts, phytohemagglutinin (PHA) blastogenesis, leukocyte adherence inhibition (LAI) after contact with 3M potassium chloride breast antigens, and blocking as measured in the blastogenesis and LAI assays. Good correlation was found between favorable clinical response to adrenalectomy and a rise in the number of absolute T cells, an increase in LAI positivity, and a decrease in blocking as measured by LAI blocking assay, but no correlation was seen in PHA blastogenesis assays. The association of clinical objective responses and improved immune responses is of significance.     

Histamine stimulation and inhibition of human cryopreserved parathyroid tissue

To elucidate the mechanism by which cimetidine, an H2 antagonist, inhibits parathormone secretion, immunoreactive cyclic AMP (cAMP) production was measured at low (0.5 mM) and normal (1.0 mM) calcium concentrations, with histamine stimulation and histamine inhibition by cimetidine, in a cell dispersion preparation from cryopreserved glands of 12 hyperparathyroid patients. At low calcium, histamine-mediated cAMP production increased from a basal level of 382 +/- 44 femtomoles/10(5) cells to 514 +/- 74 femtomoles/10(5) cells (P less than 0.05). Cimetidine inhibition of histamine-stimulated parathyroid cells at low calcium resulted in a decrease in cAMP production from 514 +/- 74 femtomoles/10(5) cells to 410 +/- 62 femtomoles/10(5) cells (P less than 0.01). At normal calcium the cAMP production in the histamine-stimulated experiment increased from a basal level of 293 +/- 66 femtomoles/10(5) cells to 477 +/- 100 femtomoles/10(5) cells (P less than 0.01) and decreased to 321 +/- 69 femtomoles/10(5) cells (P less than 0.01) in the histamine and cimetidine experiment. Stimulation by isoproterenol, a beta-adrenergic agonist, at low calcium in the histamine-primed group showed an increase in cAMP production from 514 +/- 74 femtomoles/10(5) cells to 639 +/- 71 femtomoles/10(5) cells (P less than 0.005). These results suggest that histamine plays an important role in cAMP production in hyperparathyroid cells and that cimetidine inhibition of histamine-stimulated cAMP production may explain the decrease of immunoreactive parathormone by this H2 antagonist reported in patients with hyperparathyroidism.     

Protamine-heparin-induced pulmonary hypertension in pigs: effects of treatment with a thromboxane receptor antagonist on hemodynamics and coagulation.

Adverse hemodynamic reactions after protamine neutralization of heparin are an infrequent but important clinical problem. Pre-treatment of swine with a thromboxane A2 receptor antagonist has been reported to prevent the pulmonary hypertensive response occasionally seen after protamine reversal of heparin anticoagulation. In the current study, a control group of pigs (n = 9) received intravenous heparin (300 IU/kg), followed after 10 min by a neutralizing dose of protamine (3 mg/kg). A treatment group of pigs (n = 11) was treated identically, except that the thromboxane A2 receptor antagonist L-670596 (2 mg/kg) was infused intravenously 2 min after the protamine infusion. Hemodynamic and coagulation profiles were monitored during these procedures. Pulmonary hypertension developed and reached a peak within 2 min of protamine administration, often at the same time that L-670596 was administered in the treatment group. There was no statistical difference between control and treatment groups' peak pulmonary arterial pressure and peak pulmonary vascular resistance. However, the interval for return of mean pulmonary artery pressure from peak to baseline values was 11.6 +/- 3.1 versus 5.5 +/- 1.9 min (mean +/- SD) for control and treatment groups, respectively (P less than 0.01). Thromboxane B2 plasma concentrations increased in both groups and were correlated with the pulmonary hypertensive response (r = 0.86, P less than 0.01). Platelet aggregation to collagen was inhibited by the thromboxane A2 receptor antagonist (P less than 0.05). Bleeding time was prolonged beyond normal range in 50% of L-670596-treated pigs. All other coagulation tests in both groups returned to baseline after reversal of heparin with protamine and were unaffected by L-670596.(ABSTRACT TRUNCATED AT 250 WORDS)     

Cimetidine protection against lethal tumor challenge in mice

Cimetidine, a histamine type-2 receptor antagonist, has been shown to augment proliferative responses of lymphocytes in man and mouse and to increase in vitro-generated murine cell-mediated cytotoxicity. It has been suggested by others that histamine receptors are involved in modulating the immune response through mediation of suppressor cell function. We have previously described a murine tumor model in which suppressor function increases with advancing tumor burden. We now have examined the in vivo effect of cimetidine on survival in this tumor-bearing murine model. Cimetidine was administered in the drinking water to C57BL/6 mice after an intraperitoneal injection of an LD90 dose of EL4 tumor cells. The survival rate was noticeably improved (56%) with an optimal dose of cimetidine (100 mg/kg/day) after 30 days, compared to that of water-treated control mice (10%). This protective effect was present with young (2 months old) as well as older (8 months old) mice. Rechallenge of cimetidine-treated survivors with a six times LD100 tumor dose and continuation of cimetidine produced a 33% survival rate. Comparison of cimetidine (100 mg/kg/day) with different doses of diphenhydramine (histamine type-1 antagonist) showed the protective effect to be more type-2 specific. The mechanism of action of cimetidine remains unclear, but based on this work and work by others, we think that cimetidine probably modulates suppressor cell function. Cimetidine may have potential as an immunomodulator.     

Mechanical strain stimulates osteoblast proliferation through the estrogen receptor in males as well as females.

Mechanical strain, testosterone, and estrogen all stimulate proliferation of primary cultures of male rat long bone (LOB)-derived osteoblast-like cells as determined by [3H]thymidine incorporation. The maximum proliferative effect of a single period of mechanical strain (3400 microepsilon, 1 Hz, and 600 cycles) is additional to that of testosterone (10(-8) M) or estrogen (10(-8) M). The cells' proliferative response to strain is abolished both by concentrations of tamoxifen that cause proliferation (10(-8) M) and by those that have no effect (10(-6) M). Strain-related proliferation also is reduced by the estrogen antagonist ICI 182,780 (10(-8) M) but is unaffected by the androgen receptor antagonist hydroxyflutamide (10(-7) M). Tamoxifen, ICI 182,780, and the aromatase inhibitor 4-dihydroandrostenedione, at concentrations that have no effect on basal proliferation, significantly reduce the proliferative effect of the aromatizable androgen testosterone but not that of the nonaromatizable androgen 5alpha-dihydrotestosterone. Hydroxyflutamide, at a concentration that has no effect on basal proliferation (10(-7) M), eliminates the proliferative effect of 5alpha-dihydro-testosterone but had no significant effect on that caused by testosterone. Proliferation associated with strain is blocked by neutralizing antibody to insulin-like growth factor II (IGF-II) but not by antibody to IGF-I. Proliferation associated with testosterone is blocked by neutralizing antibody to IGF-I but is unaffected by antibody to IGF-II. These data suggest that in rat osteoblast-like cells from males, as from females, strain-related proliferation is mediated through the estrogen receptor (ER) in a manner that does not compete with estrogen but that can be blocked by ER modulators. Proliferation associated with testosterone appears to follow its aromatization to estrogen and is mediated through the ER, whereas proliferation associated with 5alpha-dihydrotestosterone is mediated by the androgen receptor. Strain-related proliferation in males, as in females, is mediated by IGF-II, whereas proliferation associated with estrogen and testosterone is mediated by IGF-I.     

Immune inhibitory effects of renal cell carcinoma extract on lectin and alloantigen-induced peripheral blood and tumor infiltrating lymphocyte blastogenesis

The presence of tumor infiltrating lymphocytes (TIL) has been attributed to the host cell mediated immune response against the evolving malignancy. However, due to specific evasive and escape mechanisms, the immune competent cells are rendered ineffective. One such mechanism may be the production of immune suppressor substance(s), inhibiting lymphocyte proliferation, and subsequently, their transformation into effector cells. To evaluate a possible impact of RCC extract on lectin and alloantigen-induced proliferation of TIL and peripheral blood lymphocytes (PBL) from renal cell carcinoma (RCC) patients and from healthy control human subjects. Tumor extract and TIL were derived from 13 patients with RCC undergoing radical nephrectomy. Tumor infiltrating lymphocytes and PBL from these patients were activated with Concanavalin A (Con-A), Phytohemoglutinine (PHA) or Pokeweed (PW) and the rate of blastogenesis was measured by (3)H Thymidine incorporation. The same procedure was used in assay with PBL from control healthy blood donors. There was a significant reduction (88.6%) in the proliferative response to ConA of TIL compared to PBL from the same patients (P = 0.007). A similar decrease was seen following stimulation by PHA (85.8%, P = 0.01) and PW mitogen (78.5%, P = 0.001). A 79.5% decrease in response level of TIL to alloantigens compared to PBL from RCC patients (P = 0.021), was observed. Lectin induced proliferative response of RCC patients was significantly lower in the presence of RCC extract (82.9%) compared to normal kidney extract (P = 0.008). Alloantigenic stimulation of healthy individual PBL was also decreased significantly in the presence of RCC extract (92.9%, P = 0.0001) compared to normal kidney extract. Similarly, lectin induced stimulation of healthy control PBL in the presence of RCC extract was significantly lower (83.2%, P = 0.003). Our data suggest that RCC extract contains an immune suppressive substance(s), capable of inhibiting lymphocyte proliferative response of tumor infiltrating lymphocytes as well as of PBL from patients and healthy individuals alike. This may be one of the mechanisms by which the tumor evades the transformation of lymphocytes into effector killer cells, and thus affects the biological inter-relationship between tumor and host. Identification of this substance and its gene may provide an effective anti-tumoral treatment modality.     

Suppressive effect of a mouse testicular extract on lymphocyte activation

The effect of mouse testicular extract (TE) on lymphocyte activation was investigated. TE, in the dose range 75-600 micrograms ml-1, suppressed significantly the blastogenic response of splenocytes to concanavalin A (Con-A), pokeweed mitogen (PWM), phytohaemagglutinin (PHA) and lipopolysaccharide (LPS). TE also suppressed the blastogenic response of B-cells to LPS and of T-cells to PHA in a dose-dependent manner as well as suppressing the mixed lymphocyte reaction (MLR). Pretreatment of splenocytes with TE did not however, completely suppress their blastogenic response to Con-A, when the treated cells were washed prior to culturing. Furthermore, TE did not inhibit the on-going blastogenesis of splenocytes that had been activated already with Con-A for 48 h. Splenocytes obtained from TE-treated mice remained capable of responding to Con-A stimulation, whereas they did not respond to listerial antigens when mice were immunized with Listeria monocytogenes together with TE. The effects of TE were enhanced significantly by heating to 100 degrees C, but were resistant to pronase, RNase and DNase. These results suggest that TE affects non-specifically the stage of lymphocyte sensitization to antigens or mitogens.     

Additive effects of calcium antagonists on cyclosporin A-induced inhibition of T-cell proliferation

The purpose of this study was to investigate possible additive effects of calcium antagonists on the cyclosporin A (CsA)-induced inhibition of cellular immunity. Human T-cells were isolated using standard methods and stimulated with phytohaemagglutinin (PHA, n = 8), the monoclonal antibody OKT3 (n = 6), or mixed lymphocyte reaction (MLR, n = 5). Verapamil, nifedipine, nimodipine or diltiazem were added (5 x 10(-7) - 5 x 10(-5) M) to the cultures, either alone, or in combination with CsA (62.5, 125, and 250 ng/ml). 3H-thymidine uptake was measured to estimate the proliferative responses and dose response curves were constructed for the Ca antagonists and their combinations with CsA. A 50% inhibition of T-cell proliferation in the different stimulation assays was achieved with 3.2 x 10(-5) - 5.3 x 10(-5) M verapamil, 2.5 x 10(-5) -4.3 x 10(-5) M nifedipine, 3.7 x 10(-6) - 5 x 10(-6) M nimodipine, and greater than 5 x 10(-5) M diltiazem. In combination with CsA a dose-dependent additive inhibitory effect of the Ca antagonists on T-cell proliferation was observed. This effect was less pronounced in the OKT3 assay, intermediate after PHA stimulation and most pronounced in MLR. Even in low concentrations, which correspond to therapeutic serum concentrations, Ca antagonists have an additive inhibitory effect in MLR. We conclude that Ca antagonists exert a dose-dependent inhibitory effect on T-cell proliferation. A combination of CsA with verapamil, nifedipine, nimodipine, or diltiazem is more effective than each drug given alone. This additive effect of Ca antagonists and CsA may possibly contribute to a better graft survival in clinical transplantation.     

Diphenhydramine prevents the haemo-dynamic changes of cimetidine in ICU patients

Cimetidine, a histamine 2 (H2) antagonist, produces a decrease in arterial pressure due to vasodilatation, especially in critically ill patients. This may be because cimetidine acts as a histamine agonist. We, therefore, investigated the effects of the histamine 1(H1) receptor antagonist, diphenhydramine, on the haemodynamic changes observed after cimetidine in ICU patients. Each patient was studied on two separate days. In a random fashion, they received cimetidine 200 mg iv on one day, and on the other, a pretreatment of diphenhydramine 40 mg iv with cimetidine 200 mg iv. In the non-pretreatment group, mean arterial pressure (MAP) decreased from 107.4 +/- 8.4 mmHg to 86.7 +/- 11.4 mmHg (P less than 0.01) two minutes after cimetidine. Also, systemic vascular resistance (SVR) decreased during the eight-minute observation period (P less than 0.01). In contrast, in the pretreatment group, little haemodynamic change was seen. We conclude that an H1 antagonist may be useful in preventing hypotension caused by iv cimetidine, since the vasodilating activity of cimetidine is mediated, in part, through the H1 receptor.     

Proliferative response of T lymphocytes to mitogenic lectins in essential hypertension

Several studies in human and experimental models indicate the existence of a partial relationship between essential hypertension (EH) and the immune system. In this study, cellular immune functions were investigated in 13 patients with untreated and uncomplicated essential hypertension (EHP) and in 10 of their offspring (EHO) and compared to 13 age- and sex-matched normotensive controls (NC) and 10 of their offspring (NCO). The total number of T cells and T cell subsets were similar in all groups examined. In the EHP, basal lymphocyte transformation without lectins was significantly lower (1,126 +/- 261 cpm of [3H]-thymidine uptake) than in the NC (3,223 +/- 736, p less than 0.01); the response to both phytohemagglutinin (PHA) and concanavalin A (ConA) revealed reduced [3H]-thymidine uptake as compared with NC (21,890 +/- 5,432 compared to 64,574 +/- 9,723 for PHA and 10,488 +/- 2,621 compared to 37,334 +/- 8,148 for ConA, respectively, p less than 0.01). However, the ability to proliferate as a response to lectins was normal. This was leading to a normal stimulation index in both groups. In the EHO, non-significant decrease in basal transformation and reduced uptake with PHA (49,537 +/- 7,478) versus NCO (69,911 +/- 7,254) and NC (64,574 +/- 9,723) were found. These findings suggest that the proliferative response of T lymphocytes is partially suppressed in EH.     

Age-dependent variation of lymphocyte function in the postoperative child

Circulating lymphocyte profiles and reactivity normally vary with age. Operation results in depression of both lymphocyte counts and blastogenesis but the relationship of age to these alterations has not been previously evaluated in the pediatric surgical patient. This report analyzes the relationship of age to lymphocyte alteration in the postoperative child. Thirty-five healthy children (age range 1 mo to 12 yr), admitted for elective herniorrhaphy, underwent perioperative lymphocyte assay. Anesthesia consisted of halothane and NO2, and operative time averaged 54 minutes. Three milliliters of heparinized whole blood was obtained at induction of anesthesia and at 2 hours postoperatively. Lymphocytes were separated by Histopaque gradient and assayed for absolute count, total T-cells, and total B-cells. Lymphocyte reactivity was determined by 3H-Thymidine incorporation during incubation with the mitogens phytohemagglutinin (PHA), pokeweed (PWM), and/or concanavalin A (Con A) and results expressed as the logarithm of scintillation counts per minute. Differences in preoperative and postoperative values were analyzed for significance by paired T-test. The same differences were evaluated for relationship to age by regression analysis. Operation resulted in significant decreases in all lymphocyte counts (absolute, T- and B-cells), and the operative-induced alteration in both absolute and total B-cell counts were significantly correlated with age (P less than .03, P less than .007, respectively). Similarly, operation resulted in significant depression of lymphocyte reactivity and alteration in B-cell response (PWM) was significantly correlated with age (P less than .008). In all instances of significant correlation, lymphocyte alterations were inversely related to age.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of serum source on protein-free diet lymphocyte blastogenesis

The influence of protein depletion on serum factors in PHA lymphocyte blastogenesis was studied in a rat model. Buffalo rats were divided randomly into two groups and fed either a protein-free (PF) diet or a regular 25% protein diet (RD). At weekly intervals, lymph node lymphocytes were cultured with PHA in either autologous or pooled 10% rat serum. For weeks 2 through 6, PHA stimulated blastogenesis of lymphocytes from rats maintained on PF diet incubated with autologous serum decreased significantly compared with RD lymphocytes cultured with RD serum. At week 4, PHA blastogenesis of PF lymphocytes cultured with RD serum was similar to that of RD lymphocytes incubated with RD serum. AT weeks 5 and 6, PHA stimulation of PF lymphocytes assayed with RD serum was depressed compared with RD lymphocytes cultured with RD. For weeks 4 through 6, blastogenesis of RD lymphocytes assayed with PF serum decreased significantly compared with RD lymphocytes incubated with RD serum. Three weeks of protein repletion of rats previously on a PF diet for 6 weeks restored PHA blastogenesis to that observed for lymphocytes from animals in the RD group. The data suggested that suppression of PHA blastogenesis of lymphocytes from rats maintained on PF diet involved a serum factor in the early stages of protein depletion and an additional defect (not serum related) in lymphocyte blastogenesis after prolonged protein depletion. In addition, this defect was corrected after a period repletion.     

Effect of histamine and histamine receptor antagonists on rat mesenteric microcirculation

Histamine release adjacent to mesenteric arterioles under conditions of ischemia causes vasodilation and increases regional blood flow. This is presumably a protective mechanism which may be blocked by the use of H1 and H2 antagonists. Mesenteric arterioles of 29 rats were observed with intravital microscopy. Diameter and erythrocyte velocity were measured and arteriolar flow was calculated. Histamine was topically applied to the vessels under view in sequentially increasing concentrations (10(-7) to 10(-4) M). Following systemic injection of an H1 or H2 receptor antagonist or ibuprofen, the application of 10(-4) M histamine was repeated. Topical histamine caused vasodilation (122% of control; P less than 0.05) at 10(-4) M with a corresponding increase in erythrocyte velocity and calculated flow (118 and 177% of control, respectively; P less than 0.05 for each). The vasodilatory effects of histamine were blocked by systemic injection of histamine receptor antagonists (H1 + H2 greater than H1 greater than H2), while ibuprofen had no significant effect. In situations in which the gut is at risk for ischemia, the use of H1 and/or H2 receptor antagonists may seriously compromise the mesenteric microcirculation.     

Paradoxical effect of trifluoperazine, a calmodulin antagonist, on pepsinogen secretion

Pepsinogen secretion (PS) is modulated at the intracellular level by both cAMP and calcium ion. Cholecystokinin octapeptide (CCK-8), a potent stimulus for PS, is believed to act through calcium. The most extensively studied pathway for calcium-mediated modulation involves the formation of calcium/calmodulin complexes, leading to activation of calmodulin. We have therefore examined the hypothesis that an inhibitor of calmodulin might inhibit PS stimulated by CCK-8. The phenothiazine derivative trifluoperazine (TFP) was chosen as a calmodulin antagonist. We measured in vitro secretion of pepsinogen by isolated gastric glands as a function of TFP concentration 10(-6) M-5 X 10(-4) M), in the presence and absence of a maximal concentration of CCK-8 (10(-7) M). Cellular viability was determined by measurement of release of the enzyme lactate dehydrogenase (LDH) into the medium. TFP did not significantly inhibit PS stimulation by CCK-8 at any concentration (P greater than 0.05). At 10(-4) M, TFP actually augmented PS stimulation by CCK-8 (P less than 0.05). TFP alone significantly stimulated PS (P less than 0.05) at 5 X 10(-5) M and above. TFP did not raise cAMP levels at any concentration tested (P less than 0.05), in contrast to the adenylate cyclase activator forskolin, 10(-5) M, which caused a 6- to 37-fold increase (P less than 0.05). TFP, 2 X 10(-4) did not increase LDH levels significantly (P less than 0.05). Thus a calmodulin inhibitor, TFP, paradoxically stimulates PS. This stimulatory effect of TFP is not cAMP-dependent and is not accompanied by a nonspecific release of LDH into the medium.(ABSTRACT TRUNCATED AT 250 WORDS)