Validity of Coat-A-Count insulin RIA kit for quantifying total and free humalog.
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Humans↗
Biomedical subjects
R R Bowsher
Publications and source records attributed to R R Bowsher.
[Lys(B28), Pro(B29)]-human insulin: effect of injection time on postprandial glycemia.
BACKGROUND: [Lys(B28), Pro(B29)]-human insulin (lispro) is an insulin analogue with a reduced capacity for self-association and faster absorption from subcutaneous injection sites. We hypothesized that administration of lispro closer to a meal would result in better glucose control than that achieved with regular insulin. METHODS: This trial used a randomized crossover design that consisted of a period of metabolic stabilization lasting 9 days followed by an evaluation period lasting 5 days. The patients received weight-maintenance diets, and insulin doses were adjusted as needed. Calorie intake, insulin dose, and activities were kept constant once the evaluation period began. During the evaluation period, we varied the time between insulin injection and mealtime and assessed glucose control. RESULTS: During the evaluation period, the lowest mean glucose concentrations were 117.9 mg/dl for lispro and 119.8 mg/dl (p = 0.817) for regular insulin. To obtain these, we gave lispro, on average, 22.5 minutes before meals and regular insulin 63.8 minutes before meals (p = 0.006). A similar pattern was evident throughout the glucose control parameters. The exception was mean amplitude of glucose excursion, which was lower after lispro (59 versus 75 mg/dl; p = 0.007) compared with regular insulin. CONCLUSIONS: We achieved equal or slightly better glucose control, as reflected by mean amplitude of glucose excursion, with insulin lispro given much closer to meal time than that achieved with regular insulin. As a result of these findings, we propose that a rapidly absorbed analogue of insulin is capable of achieving better control of postprandial glucose at a more convenient injection time.
Adult↗
Changes in IGF-I and -II expression and secretion during the proliferation and differentiation of normal rat osteoblasts.
IGF-I and -II have potent effects on proliferation and differentiation of osteoblasts in vitro. These cells secrete both IGFs and expression of these peptides is regulated by several of the hormones and growth factors that promote bone resorption and/or formation. However, the physiological role(s) of IGFs in the remodelling process of adult bone is still unclear. Some confusion may arise from results influenced, in part, by differences in the state of osteoblast development of in vitro cultures. Several laboratories have demonstrated that murine osteoblast cultures progress from proliferating preosteoblasts, to mature differentiated osteoblasts that form an extracellular matrix, to cultures that form a mineralized matrix. We have recently documented changes in IGF-binding protein expression and secretion in these cultures. To complement and extend this work, we have examined IGF-I expression and secretion and IGF-II expression during in vitro osteoblast development. Steady-state mRNA levels of both IGF-I and -II increased from the earliest time examined, day 5 in culture, to a maximum at day 11 and, thereafter, declined. IGF-I secreted into the medium also changed in a biphasic manner, but IGF-II could not be quantitated due to the sensitivity of our assay. Secretion of IGF-I was lowest between days 8 and 14. IGF-I secretion on day 5 was significantly greater than day 8. Similarly, IGF-1 secretion from day 17 to 26 was also greater than observed for days 8 to 14. If differentiation of the cells was inhibited, this late rise in IGF-I secretion was abolished.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
Higher proinsulin and specific insulin are both associated with a parental history of diabetes in nondiabetic Mexican-American subjects.
Both insulin resistance and decreased insulin secretion have been hypothesized to be precursors of non-insulin-dependent diabetes. An elevated proinsulin concentration reflects abnormal proinsulin processing and could indicate abnormal insulin secretion. We examined fasting insulin (measured by a radioimmunoassay that does not cross-react with proinsulin), as a marker of insulin resistance, and proinsulin and the fasting proinsulin-to-insulin ratio, as markers of impaired proinsulin processing, in 597 nondiabetic Mexican-Americans from the San Antonio Heart Study. Fasting insulin, proinsulin, and the fasting proinsulin-to-insulin ratio were higher in subjects with a parental history of diabetes than in subjects without such a history. These differences remained statistically significant after adjustment for obesity, body fat distribution, and glucose tolerance. A parental history of diabetes in nondiabetic Mexican-Americans is associated with an increase in fasting specific insulin and a disproportionate increase in proinsulin relative to insulin. These data suggest that both increased insulin resistance and abnormal processing of proinsulin are present in offspring of parents with diabetes.
Blood Glucose↗
Humalog, a rapidly absorbed analog of human insulin, determined with Coat-A-Count insulin radioimmunoassay.
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Humans↗
Fialuridine accumulates in DNA of dogs, monkeys, and rats following long-term oral administration.
Accumulation of the antiviral nucleoside analogue fialuridine (FIAU; 1-(2'-deoxy-2'-fluoro-beta-D-arab-inofuranosyl-5-iodouracil) in genomic DNA was examined with a modified version of a recently developed RIA for FIAU. DNA was obtained from tissues of dogs administered FIAU at 0, 1, 2, or 3 mg/kg of body weight per day for 90 days, monkeys administered FIAU at 0 or 25 mg/kg per day for 30 days, and rats administered FIAU at 0, 255, or 510 mg/kg per day for 70 days. FIAU incorporation was observed in all species. In the rat, FIAU was incorporated into DNA of all tissues examined, with highest concentrations in the liver followed by jejunum, spleen, and heart. FIAU was also incorporated into sperm DNA. Incorporation rates were as high as 11,000 pmol of FIAU per mumol of thymidine or 1 FIAU molecule per 90 thymidine molecules. In dogs and rats, the extent of incorporation was dose-dependent. Across species, FIAU concentrations in DNA were not singly dependent on the total dose administered but also may have been dependent on the duration of exposure. These studies show that FIAU accumulates to high concentrations in genomic DNA of liver as well as other tissues during chronic oral administration and suggest that net accumulation of FIAU in DNA may be a critical step in FIAU-induced toxicity.
Administration, Oral↗
Sensitive and specific radioimmunoassay for fialuridine: initial assessment of pharmacokinetics after single oral doses to healthy volunteers.
Fialuridine (FIAU) is a halogen-substituted analog of thymidine that was undergoing clinical investigation as a drug for the treatment of chronic hepatitis B viral infection. However, clinical trials of FIAU were terminated after adverse events occurred following chronic oral administration. Prior to the termination of clinical trials, a sensitive assay was needed for the measurement of FIAU because of the anticipated low dose administered to patients. We therefore undertook the development of a radioimmunoassay (RIA). A specific antiserum was raised in rabbits following immunization with a 5'-O-hemisuccinate analog of FIAU coupled to keyhole limpet hemocyanin. Radiolabeled FIAU was synthesized by a destannylation procedure by using sodium [125I]iodide. We developed a competitive-binding procedure and used precipitation with polyethylene glycol as the method for separating the bound and free forms of FIAU. The RIA is sensitive (0.2 ng/ml), specific (negligible interference from known metabolites and endogenous nucleosides), and reproducible (interassay coefficients of variation range from 5 to 19.7% for serum controls). We used the RIA to assess the pharmacokinetics of FIAU in healthy adult volunteers following administration of a single 5-mg oral dose. The sensitivity of the RIA permitted the detection of a prolonged elimination phase for FIAU in healthy volunteers and dogs, with mean elimination half-lives of 29.3 and 35.3 h, respectively. We conclude the RIA is a valid method for the quantification of FIAU in biological fluids.
Administration, Oral↗
Disproportionately increased proinsulin levels are associated with the insulin resistance syndrome.
Recent data suggest that proinsulin may be associated with increased cardiovascular risk factors in both diabetic and nondiabetic subjects. We examined the relation of insulin, proinsulin, and the fasting proinsulin/insulin ratio to a number of metabolic disorders believed to be related to the insulin resistance syndrome (low high density lipoprotein cholesterol and high triglyceride levels, hypertension, and impaired glucose tolerance). Proinsulin was measured by a RIA, and insulin was measured by a Linco RIA that does not cross-react with proinsulin. The increased fasting proinsulin/insulin ratio was significantly associated with hypertension, low high density lipoprotein cholesterol and high triglyceride levels, and impaired glucose tolerance in 423 nondiabetic subjects. The fasting proinsulin/insulin ratio increased significantly with the number of metabolic disorders (zero, 0.060; one, 0.086; two, 0.098; three, 0.177; four, 0.182; P < 0.001). The increased proinsulin/insulin ratio was also associated with a greater number of metabolic disorders in diabetic subjects. Our results show that particularly nondiabetic individuals with the insulin resistance syndrome not only have hyperinsulinemia as a marker of insulin resistance, but also show an increase in proinsulin relative to insulin, which may reflect relative beta-cell failure or malfunction.
Anthropometry↗
Proinsulin and specific insulin concentration in high- and low-risk populations for NIDDM.
Hyperinsulinemia and insulin resistance have been implicated as risk factors for the development of non-insulin-dependent diabetes mellitus (NIDDM). Recent data suggest that proinsulin may comprise a large proportion of immunoreactive insulin in subjects with NIDDM and possibly in those with impaired glucose tolerance (IGT) as well. Increased proinsulin concentrations are thought to be an early indicator of a failing pancreas. We examined proinsulin, insulin (using an assay that does not display appreciable cross-reactivity with proinsulin), and the fasting proinsulin:insulin ratio in 206 nondiabetic Mexican-American (a high-risk population for NIDDM) and 123 nondiabetic non-Hispanic white (a low-risk population for NIDDM) participants in the San Antonio Heart Study, a population-based study of diabetes and cardiovascular disease. Mexican-Americans had significantly higher fasting and 2-h proinsulin and insulin levels but similar fasting proinsulin:insulin ratios compared with non-Hispanic whites. After statistical adjustment for age, body mass index, waist-to-hip ratio, and glucose tolerance status, Mexican-Americans continued to have higher fasting and 2-h insulin and fasting and 2-h proinsulin concentrations but similar proinsulin:insulin ratios compared with non-Hispanic whites. The fasting proinsulin:insulin ratio was higher in 85 subjects with NIDDM compared with subjects with IGT or normal glucose tolerance (0.31, 0.09, and 0.07, respectively). Thus, nondiabetic subjects from a high-risk population for NIDDM are hyperinsulinemic (using an assay that does not cross-react with proinsulin) and, further, do not secrete more proinsulin relative to insulin itself than do nondiabetic subjects from a low-risk population.
Diabetes Mellitus, Type 2↗
[Lys(B28), Pro(B29)]-human insulin. A rapidly absorbed analogue of human insulin.
[Lys(B28, Pro(B29)]-human insulin (LYSPRO) is an insulin analogue in which the natural amino acid sequence of the B-chain at positions 28 and 29 is inverted. These changes result in an insulin molecule with a greatly reduced capacity for self-association in solution. These clinical studies were designed to compare LYSPRO with human Regular insulin after subcutaneous injection in humans. We wanted to evaluate the effect of adding zinc to LYSPRO on its pharmacokinetics and pharmacodynamics. In addition, we compared the pharmacokinetics and pharmacodynamics of LYSPRO and human Regular insulin after subcutaneous injection to those of human Regular insulin given intravenously. Thus, we compared four treatments: solutions of zinc-free LYSPRO given subcutaneously (A), zinc-containing LYSPRO given subcutaneously (B), human Regular insulin given subcutaneously (C), and human Regular insulin given intravenously (D). We gave a 10-U dose of each treatment to 10 healthy (nondiabetic) men during glucose clamps. Serum insulin concentrations peaked more than two times higher (maximum serum insulin level [Cmax], 698 vs. 308 pM, A vs. C) and in less than half the time (time to Cmax [Tmax], 42 vs. 101 min, A vs. C) after subcutaneous injection of zinc-free LYSPRO. At the same time, the glucose infusion rate peaked in about half the time (time to maximum glucose infusion rate [TRmax], 99 vs. 179 min, A vs. C) and was slightly but not significantly higher (maximum glucose infusion rate [Rmax], 3.1 vs. 2.2 mmol/min, A vs. C) than that of human Regular insulin.(ABSTRACT TRUNCATED AT 250 WORDS)
Adult↗
Establishment of time-action profiles for regular and NPH insulin using pharmacodynamic modeling.
OBJECTIVE: To provide distinct definitions and quantify the establishment of onset, peak, and duration of action for insulins. RESEARCH DESIGN AND METHODS: We administered single subcutaneous doses of 10 U regular insulin to 10 volunteer subjects and 25 U NPH insulin to 6 healthy male volunteer subjects on separate occasions. Each dose was given after an overnight fast during a glucose clamp to maintain an euglycemic state. We measured serum insulin concentrations and glucose infusion rates (GIR) from frequent blood sampling after each treatment. Serum insulin concentrations were related to GIR values at each collection time and a counter-clockwise hysteresis resulted. An effect compartment model was used to simultaneously describe the pharmacokinetics and pharmacodynamics of each insulin and to resolve the hysteresis. RESULTS: From the resulting relationship, GIR could then be predicted, with onset and duration of action reflecting the time when effect compartment concentrations initially exceeded then declined below a 10% maximum possible effect (Emax) level. Ninety-five percent confidence intervals were constructed allowing a predictive range of values. For regular insulin, a mean onset of 0.75 h, peak of 2 h, and duration of 6 h was estimated. Mean values were also produced with NPH, with an onset of 3 h, peak of 6-7 h, and a duration of 13 h estimated. CONCLUSIONS: This method estimates the onset, peak, and duration of insulin action. Although these estimates were from single doses, we believe they can provide good estimations of insulin activity.
Adult↗
Comparative pharmacokinetics and glucodynamics of two human insulin mixtures. 70/30 and 50/50 insulin mixtures.
OBJECTIVE: To compare and contrast the pharmacokinetics and glucodynamics of two insulin mixtures, one of 50% NPH human insulin and 50% Regular human insulin (50/50) and one of 70% NPH human insulin and 30% Regular human insulin (70/30), in healthy male volunteers after subcutaneous administrations of 0.3 U/kg. RESEARCH DESIGN AND METHODS: We administered single doses of 50/50 and 70/30 insulins to 18 volunteers in a randomized crossover fashion. All subjects received 0.3 U/kg of each mixture separated by at least 7 days. Each dose was given after an overnight fast and during a glucose clamp to maintain a euglycemic state. We measured serum insulin and C-peptide concentrations through frequent blood sampling after each treatment. Pharmacokinetic measurements were calculated from insulin data corrected for C-peptide, including maximum insulin concentration (Cmax), time to maximum insulin concentration (tmax), terminal rate constant (beta), area under the curve from 0 to infinity (AUCinfinity0), and mean residence time (MRT). Pharmacodynamic measurements were summarized from C-peptide concentrations (minimum C-peptide concentration [Cmin], time to minimum C-peptide concentration [tmin], area between the C-peptide baseline and the C-peptide suppression curve [AOCc], absolute maximal difference from baseline [Sdiff] and glucose clamp measurements. The glucose clamp measurements included maximum infusion rates (Rmax) and time to Rmax (TRmax) from glucose infusion rate (GIR) documentation, as well as cumulative glucose infused during the first 4 h ((0)4Gtot) and total glucose infused (Gtot) during the study. RESULTS: For the pharmacokinetic assessment, statistically greater values of insulin Cmax and beta were found for the 50/50 mixture, whereas the 70/30 mixture had a greater MRT. Statistical differences were also detected in glucodynamics, with greater values of Rmax and (0)4Gtot found with the 50/50 mixture. Notably, differences were not detected for insulin AUCinfinity0 and Gtot values. CONCLUSIONS: Higher insulin concentrations and a greater initial response were present with the 50/50 mixture, but the two mixtures had equivalent bioavailability and cumulative effects. These results support use of the 50/50 mixture in situations where greater initial glucose control is required.
Adult↗
Improved HPLC-radioimmunoassay for quantifying angiotensin II in plasma.
To measure the octapeptide angiotensin II (Ang II) in plasma, we developed a sensitive, specific assay that interfaces solid-phase extraction, HPLC, and RIA. A reversed-phase HPLC system involving isocratic elution at 38 degrees C with a volatile mobile phase of acetonitrile and the ion-pairing reagent heptafluorobutyric acid produced baseline separation of angiotensin peptides. Ang II was collected as a single fraction, concentrated by evaporation to dryness, and measured by RIA after resuspension in RIA buffer. Even including column washing between sample injections to prevent carryover of plasma constituents, two plasma extracts could be processed per hour by HPLC. Assay validation experiments demonstrated < 2% cross-reactivity with Ang II-related peptides; a 75% recovery from plasma at physiological concentrations of Ang II; intra- and interassay precision (CVs) of 6.2% and 10.3%, respectively; and a lower limit of quantification of 1.3 ng/L. Two clinical protocols designed to measure plasma Ang II concentration under basal and stimulated conditions confirmed the utility of the assay.
Adult↗
GABA receptors in the region of the dorsomedial hypothalamus of rats regulate anxiety in the elevated plus-maze test. II. Physiological measures.
In the previous report, we had shown that blockade and enhancement of GABAA receptors in the DMH of rats increased or decreased the level of anxiety, respectively, as measured by the elevated plus-maze test. The present study was conducted to assess the effects of enhancing GABAA neurotransmission in the DMH of rats on the physiological concomitants of anxiety such as increases in heart rate (HR), blood pressure (BP) and plasma norepinephrine (NE) levels while the animals were placed on the elevated plus-maze. Male Sprague-Dawley rats were equipped with arterial and venous catheters and stereotaxically implanted with microinjection cannulae in the cardiostimulatory region of the DMH where injection of bicuculline methiodide (BMI) elicited increases in heart rate under anesthesia. After recovery, rats were injected with either saline or the GABAA agonist muscimol and their HR, BP and plasma NE responses were measured when confined in the open or the closed arm of the elevated plus-maze. Injection of muscimol into the DMH reduced the increases seen in HR, BP and plasma NE when the rats were confined to either the closed or the open arms in addition to decreasing 'anxiety' in the plus-maze. Injection of muscimol into the areas of the hypothalamus surrounding the DMH did not significantly affect the changes in HR, BP and plasma NE in the plus-maze. Blocking the changes in HR and BP elicited by microinjecting GABAergic drugs into the DMH of rats, with systemic injections of a combination of atropine and the beta-blocker atenolol, did not block the behavioral effects of the GABAergic drugs in the plus-maze test.
Animals↗
Effect of tibenelast (a phosphodiesterase inhibitor) and theophylline on isoproterenol-stimulated heart rate, cyclic AMP and norepinephrine levels.
The effect of the phosphodiesterase inhibitors (tibenelast, theophylline) and placebo on isoproterenol-induced changes in heart rate, cAMP and norepinephrine levels in normal male volunteers was studied. Heart rates in response to isoproterenol dosing were fitted by linear regression, and horizontal shifts in the regression lines were examined between the three treatments. The shift of the regression line after placebo compared to the preplacebo line was to the right by 2.6 +/- 2.2 ng ISO/kg/min, theophylline pretreatment shifted this line to the left by 2.4 +/- 1.8 ng/kg/min (p < 0.05) and tibenelast by 3.7 +/- 1.9 ng/kg/min (p < 0.02). Both tibenelast and theophylline increased the heart rate response to isoproterenol infusion, whereas norepinephrine and cAMP levels were not different in any treatment.
Adult↗
Relationship of proinsulin and insulin to cardiovascular risk factors in nondiabetic subjects.
Recent data suggest that proinsulin is strongly associated with cardiovascular risk factors in diabetic subjects. However, this relationship has not been examined in nondiabetic subjects. Therefore, we examined the relation of proinsulin to lipids, obesity (body mass index), and waist-to-hip ratio in 260 nondiabetic individuals from the San Antonio Heart Study, a population-based study of diabetes and cardiovascular disease. Proinsulin was measured by radioimmunoassay, and insulin was measured by a Linco radioimmunoassay that does not cross-react with proinsulin. Fasting insulin was significantly associated with body mass index (0.42), waist-to-hip ratio (r = 0.30), triglyceride (r = 0.29), high-density lipoprotein cholesterol (r = -0.20), and systolic blood pressure (r = 0.16) but not significantly related to diastolic blood pressure (r = 0.11). Fasting proinsulin was significantly associated with body mass index (r = 0.19), waist-to-hip ratio (r = 0.25), triglyceride (r = 0.41), systolic blood pressure (r = 0.19), and diastolic blood pressure (r = 0.15). Proinsulin was more strongly related to increased triglyceride than insulin despite its weaker relationship to obesity. In multivariate analyses, proinsulin continued to be significantly related to triglyceride concentrations (explaining 23.1% of the variance) and to systolic blood pressure (explaining 4.0% of the variance), even after adjusting for insulin. These observations suggest that proinsulin should be measured in addition to insulin in epidemiological studies. Proinsulin may be a marker for metabolic decompensation in prediabetic subjects.
Adult↗
The interaction of norepinephrine excretion with blood pressure and race in children.
OBJECTIVE: The purpose of this study was to examine the relationship between urinary norepinephrine excretion and blood pressure, and to determine the influence of race on this relationship. Urinary norepinephrine was used to estimate renal and systemic sympathetic nervous system (SNS) activity. DESIGN: Fifty black and forty-nine white normotensive children aged 9-14 years had their blood pressure measured, and provided an overnight urine sample. METHODS: Urinary norepinephrine was measured by radioenzymatic assay. Excretion rates of norepinephrine were expressed per milligram urinary creatinine. RESULTS: Black children had age-adjusted mean diastolic and systolic blood pressure which was higher than in white children. For both blacks and whites, nocturnal urinary norepinephrine excretion rates were positively related to age-adjusted mean diastolic blood pressure, but not to systolic blood pressure. Norepinephrine excretion was significantly lower in black children compared with white children. CONCLUSION: These findings suggest that the higher blood pressures in black children were not causally related to greater SNS activity. The SNS may have been suppressed in black children, possibly by a greater expansion of plasma volume, alternatively, black children may have been more sensitive to the influences of the SNS than white children.
Adolescent↗
A rapid and sensitive radioimmunoassay for the measurement of proinsulin in human serum.
RIA methodology is used widely to measure proinsulin in human serum. However, some RIAs lack the sensitivity necessary to quantify proinsulin in unextracted serum and require long incubation periods. We developed an RIA with a sensitivity of 3.5 pM that permits the routine measurement of proinsulin in less than 48 h. This was accomplished by using a nonequilibrium binding reaction at room temperature and PEG-assisted second antibody precipitation as the method for separating bound and free proinsulin. We obtained a specific antiproinsulin antibody by absorbing the initial goat antiserum with human C-peptide-agarose. Proinsulin produced 50% displacement of tracer at 25.6 pM, whereas both human insulin and C-peptide failed to displace tracer at concentrations as high as 1 microM. We evaluated several cleaved derivatives of proinsulin for cross-reactivity with the antibody. B-chain-C-peptide cleaved derivatives (less than or equal to 50% cross-reactivity) were more potent than A-chain-C-peptide cleaved derivatives (less than 5% cross-reactivity). However, all derivatives cleaved in the region from 56-60 failed to cross-react with the antiserum. These data indicate that a major antigenic determinant is present on the C-peptide region of proinsulin adjacent to the A-chain-C-peptide junction. After administration of an oral glycemic challenge, the mean fasting serum concentration of proinsulin in normal adults rose from 4.1 +/- 0.28 to 23.6 +/- 3.8 pM. We found a significant difference in the proinsulin concentrations in 6 adults before and after a glycemic challenge when two different antibodies were used in the RIA.(ABSTRACT TRUNCATED AT 250 WORDS)
C-Peptide↗