Different effects of glucose and glyburide on insulin secretion in rat pancreatic islets pre-exposed to interleukin-1 beta. Possible involvement of K+ and Ca2+ channels

In vitro islet exposure to interleukin 1 beta inhibits the beta-cell response to glucose. We have studied whether a similar inhibition also occurs in response to the sulphonylurea glyburide. Rat pancreatic islets were cultured for 24 h in the presence or absence of 50 U/ml interleukin 1 beta and then stimulated with either glucose or glyburide for 1 h at 37 degrees C. In control islets basal insulin secretion was 117 +/- 32 pg.islet-1.h-1 (mean +/- SEM, n = 7) and greatly increased in response to 16.7 mmol/l glucose (2140 +/- 293) or 10 mumol/l glyburide (1464 +/- 234). When islets were pre-exposed to interleukin 1 beta, insulin release was significantly reduced in response to glucose (323 +/- 80, p < 0.001) but not in response to glyburide (1316 +/- 185). Since both glucose and glyburide influence beta-cell K+ and Ca2+ efflux, to further investigate this different response in islets exposed to interleukin 1 beta we measured both Rb+ efflux (as index of the ATP-sensitive K+ channel activity) and Ca2+ uptake. In control islets, the increased insulin secretion in response to 16.7 mmol/l glucose or 10 mumol/l glyburide was associated with a reduction of 86Rb efflux (decrement of -50 +/- 1.2% and -49 +/- 2.3%, respectively, mean +/- SEM, n = 5). In contrast, in interleukin 1 beta pre-exposed islets both glucose and glyburide stimulation only slightly modified 86Rb efflux (decrement of -19 +/- 1.9% and -5.3 +/- 3.1%, respectively, n = 5, p < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Glucose modulates glucose transporter affinity, glucokinase activity, and secretory response in rat pancreatic beta-cells

Pancreatic islets were cultured for 24 h in medium containing either low (1.4), normal (5.5), or high (16.7 mM) glucose, and then insulin secretion was measured at the end of 1 h incubation at 37 degrees C. Insulin release in the absence of glucose was 64 +/- 20, 152 +/- 11, and 284 +/- 30 pg.islet-1.h-1 (mean +/- SE, n = 6, G1.4 and G16.7 vs. G.5.5, P < 0.05) and the response to 22 mM glucose stimulation was 640 +/- 136, 2460 +/- 276, and 1890 +/- 172 pg.islet-1.h-1, respectively (n = 6, G1.4 vs. G5.5, P < 0.01, G16.7 vs. G5.5, P = 0.065). The 50% maximal response of insulin secretion (increment over baseline) was reached at an average glucose concentration of 9.9 +/- 0.7 mM in islets preexposed to G5.5, and at glucose 13.3 +/- 0.9 and 4.8 +/- 0.4 mM (P < 0.05 in respect to G5.5) in islets preexposed to G1.4 and G16.7, respectively. To investigate the molecular mechanism responsible for this altered glucose sensitivity, we measured, in parallel experiments, the kinetic characteristics of glucose transport, glucokinase, and glucose utilization. Glucose transport was measured by evaluating 3-O-methylglucose uptake. The apparent Km of the low-affinity transporter (GLUT2) was 16.6 +/- 2.4 mM in isolated pancreatic cells cultured at 5.5 mM glucose.(ABSTRACT TRUNCATED AT 250 WORDS)

Glyburide and tolbutamide induce desensitization of insulin release in rat pancreatic islets by different mechanisms

Insulin secretion was studied in rat pancreatic islets after 24-h exposure to various glyburide or tolbutamide concentrations. Glucose-induced insulin release was significantly (P < 0.05) reduced in islets cultured with 0.1 microM glyburide or 100 microM tolbutamide (2098 +/- 187, 832 +/- 93, and 989 +/- 88 pg/islet.h in control, glyburide-exposed, and tolbutamide-exposed islets, respectively). When glyburide-treated islets were stimulated with glyburide or tolbutamide, insulin release was also impaired compared to that in control islets (P < 0.05). In contrast, tolbutamide-exposed islets showed an impaired response to tolbutamide, but a normal response to glyburide. To investigate the mechanism of the sulfonylurea-induced impairment of insulin secretion, we measured insulin release and Rb+ efflux (a marker of the K+ channel activity) in a perifusion system and islet Ca2+ uptake under static conditions. Insulin release in response to 16.7 mM glucose increased in control islets from 9.4 +/- 1.1 to 131 +/- 19 pg/islet.min (first phase secretion peak). Simultaneously, the fractional 86Rb+ efflux declined from 0.015 +/- 0.002% to 0.006 +/- 0.001% (change in decrement, -63.5%). Glucose-induced insulin release in glyburide- and tolbutamide-treated islets was significantly reduced (first phase peak, 22.1 +/- 5 and 39.7 +/- 8 pg/islet.min, respectively; P < 0.05), and the fractional 86Rb+ efflux decrement was -21 +/- 6% for glyburide (P < 0.005 vs. control islets) and -65 +/- 4% (not different from control) for tolbutamide. When glyburide- or tolbutamide-exposed islets were stimulated with the corresponding sulfonylurea, insulin release was impaired compared to that in control islets (P < 0.05), but, again, 86Rb+ efflux was impaired (P < 0.05) only in glyburide-exposed islets. When 45Ca2+ uptake was studied, the increase in glucose concentration from 2.8 to 16.7 mM increased calcium uptake in control islets from 1.76 +/- 0.58 to 7.27 +/- 1.36 pmol/islet.2 min (n = 4). Preexposure to 0.1 microM glyburide did not change calcium uptake at a glucose concentration of 2.8 mM (1.44 +/- 0.45 pmol/islet.2 min) but significantly reduced calcium uptake stimulated by 16.7 mM glucose (3.21 +/- 0.35 pmol/islet.2 min; n = 4; P < 0.005 compared to control islets). In contrast, preexposure to 100 microM tolbutamide did not change either basal or glucose-stimulated calcium uptake (1.44 +/- 0.45 and 6.90 +/- 0.81 pmol/islet.2 min, respectively; n = 4). These data show that in vitro chronic exposure of pancreatic islets to the sulfonylureas glyburide and tolbutamide impairs their ability to respond to a subsequent glucose or sulfonylurea stimulation.(ABSTRACT TRUNCATED AT 400 WORDS)

Nicotinamide partially reverses the interleukin-1 beta inhibition of glucose-induced insulin release in pancreatic islets

Interleukin-1 beta (IL-1 beta) is known to inhibit glucose-induced insulin release by pancreatic islets. We studied the effect of nicotinamide, an inhibitor of poly[adenosine diphosphate (ADP)-ribose] synthetase and a free-radical scavenger, on this IL-1 beta-induced inhibition using rat pancreatic islets. In static experiments, groups of five islets were incubated for 24 hours in culture medium CMRL-1066, with or without 50 U/mL IL-1 beta, in the presence or absence of nicotinamide (dose range, 0 to 50 mmol/L), and then exposed for 1 hour to either 1.4 or 19.4 mmol/L glucose, 10 mmol/L arginine, or 10 mumols/L glyburide. Basal insulin secretion was 183 +/- 32 pg/islet/h (mean +/- SE, n = 7) and 176 +/- 39 (n = 7) in control islets and in islets exposed to 50 U/mL IL-1 beta, respectively. Glucose-stimulated insulin secretion was significantly reduced (185 +/- 41) in IL-1 beta-exposed islets in comparison to control islets (2,037 +/- 363). In parallel, arginine-stimulated insulin release was inhibited by IL-1 beta exposure (166 +/- 31 pg/islet/h, mean +/- SE, n = 3) in comparison to control islets (1,679 +/- 307). In contrast, IL-1 beta exposure did not significantly reduce glyburide-induced insulin secretion (1,516 +/- 231 and 1,236 +/- 214 in control and IL-1 beta-exposed islets, respectively; mean +/- SE, n = 3). When islets were simultaneously exposed to IL-1 beta and increasing concentrations of nicotinamide, a dose-dependent recovery of glucose-induced insulin secretion was observed, with the maximum effect at 25 mmol/L nicotinamide (1,007 +/- 123, P less than .001).(ABSTRACT TRUNCATED AT 250 WORDS)

Glucose regulates both glucose transport and the glucose transporter gene expression in a hamster-derived pancreatic beta-cell line (HIT)

We studied the effect of chronic exposure to high glucose on the glucose transport regulation in hamster pancreatic Beta cells in permanent culture (HIT). Cells were exposed to either 5.5 mmol/l or 16.7 mmol/l glucose for 48 h and then glucose transport was studied by measuring the (3H)-2-deoxyglucose uptake for 5 and 10 min at 37 degrees C. The 2-deoxyglucose uptake was lower in cells pre-exposed to glucose 16.7 mmol/l for 48 h compared to cells pre-exposed to 5.5 (12.0 +/- 1.6 vs 19.1 +/- 1.2 nmol/0.1 mg after 5 min, and 22.2 +/- 2.6 vs 39.0 +/- 2.9 after 10 min respectively, mean +/- SEM, n = 5, p less than 0.01). In order to investigate the mechanism(s) for glucose impairment of glucose transport, we studied the glucose carrier gene expression in the same cells by Northern and slot-blot analysis. When total RNA was extracted from HIT cells cultured at either 5.5 or 16.7 mmol/l glucose and then hybridized to 32P-labelled cDNA probes for the glucose transporter 1, the glucose transporter 2 and beta-actin, a significant reduction of both glucose transporter 1 (-63.9 +/- 4.1%, mean +/- SEM, n = 3) and glucose transporter 2 (-48.9 +/- 3.2%) mRNA was observed in HIT cells cultured with high glucose. In the same experiments no change of beta-actin mRNA was observed, suggesting that the effect of high glucose was specific on the glucose-transporter mRNAs.(ABSTRACT TRUNCATED AT 250 WORDS)

Chronic exposure to glibenclamide impairs insulin secretion in isolated rat pancreatic islets

We investigated the effect of 24 h exposure to 100 nmol/l glibenclamide on insulin secretion in isolated rat pancreatic islets. The insulin content was similar in control islets and in islets preincubated with 100 nmol/l glibenclamide for 24 h. In islets preexposed to glibenclamide: 1) the subsequent response to a maximal glibenclamide stimulatory concentration (10 mumol/l, 1 h at 37 C) was greatly reduced in comparison to control islets (0.69 +/- 0.20% vs 2.16 +/- 0.41%; mean +/- SE; n = 14; p less than 0.001); 2) the response to 100 mumol/l tolbutamide stimulation was also reduced (0.55 +/- 0.15% vs 2.38 +/- 0.44%; n = 8; p less than 0.001); 3) the response to 16.7 mmo/l glucose, both in the presence or in the absence of 1 mmol/l IBMX, a phosphodiesterase inhibitor, was also diminished by about 50% (1.79 +/- 0.39% vs. 3.22 +/- 0.42%; n = 14, p less than 0.001). In glibenclamide pretreated islets, blunted responses to stimuli were confirmed also by dynamic studies using a perifusion system. The effect of glibenclamide preincubation was fully reversible: when islets cultured in the presence of glibenclamide were transferred to a glibenclamide-free medium for further 24 h, insulin release in response to glibenclamide stimulation returned to control values. We conclude that prolonged exposure of rat pancreatic islets to glibenclamide induces a reversible desensitization to a variety of metabolic stimuli. The inhibition by prolonged glibenclamide exposure of a common pathway in the mechanism of insulin release is one possible explanation for these results.

Chronic exposure to high glucose and impairment of K(+)-channel function in perifused rat pancreatic islets

Prolonged exposure to high glucose levels impairs the ability of pancreatic islets to secrete insulin as a response to that stimulus. Because glucose, like other insulin secretagogues, elicits insulin secretion by inhibiting the ATP-sensitive K+ channels, in this study, we investigated the effect of prolonged (24-h) exposure of rat pancreatic islets to high (16.7 mM) glucose concentration on 86Rb efflux (used as a tracer for K+). The data obtained indicate that islets exposed to high glucose concentration have impaired function of the glucose-sensitive K+ channel, this phenomenon is temporarily related to a defective response of glucose-induced insulin release, and these alterations are reversible.

Effects of high glucose on insulin secretion by isolated rat islets and purified beta-cells and possible role of glycosylation

We investigated the effect of 24 h of exposure to various glucose concentrations on insulin secretion by isolated rat pancreatic islets and purified rat beta-cells. Compared with islets cultured with standard medium (5.5 mM glucose), islets cultured with 16.7 mM glucose showed a higher basal insulin release (means +/- SE, 3.0 +/- 0.5 vs. 0.7 +/- 0.2%, n = 8, P less than .005) and reduced glucose-stimulated insulin secretion (2.4 +/- 0.3 vs. 5.8 +/- 0.4%, n = 8, P less than .005). Similar results were also obtained with purified beta-cells. The effect of high glucose was time dependent (present after 12 h, maximal after 24 h) and reversible: when islets cultured with high glucose were transferred to standard medium, normal responsiveness to glucose was restored within 8 h and normal basal release within 24 h. Mannitol, 3-O-methylglucose, and 2-deoxyglucose were not able to mimic the effects of glucose. Islets or purified beta-cells cultured in the presence of high glucose had a normal response when stimulated with glyburide, dibutyryl cyclic AMP, and isobutylmethylxanthine. Tunicamycin, an inhibitor of N-terminal glycosylation, prevented glucose-induced desensitization when added during 24 h of islet culture with 16.7 mM glucose. Swainsonine, another agent that influences glycosylation, had a similar effect. Our study indicates 1) that 24 h of exposure to high glucose induces a specific and reversible impairment of insulin secretion in response to glucose, 2) that this is a direct effect of glucose on beta-cells, and 3) that islet glucose metabolism and glycosylation processes may play a critical role in determining glucose desensitization.

Metformin enhances certain insulin actions in cultured rat hepatoma cells

The effect of the oral antidiabetic agent metformin on insulin regulation of glycogen metabolism, tyrosine-aminotransferase activity, and [1-14C]aminoisobutyric acid uptake was studied in H4IIE cultured rat hepatoma cells. Metformin enhanced both basal (from 0.213 +/- 0.016 to 0.262 +/- 0.024 nmol/mg protein, p less than 0.01) and insulin stimulated [3H] glucose incorporation into glycogen in a time-dependent and dose-dependent manner. A small effect of metformin was seen at 1 mumol/l, and its greatest effects were obtained at 10 mumol/l. At the same concentrations, metformin did not influence basal tyrosine-aminotransferase activity but it potentiated insulin stimulated tyrosine-aminotransferase activity (+29.2 +/- 1.4%, p less than 0.01) and prevented the loss of tyrosine-aminotransferase responsiveness to insulin in H4IIE cells desensitised by a previous exposure to insulin. In contrast, metformin had no effect on basal or insulin-stimulated [1-14C]aminoisobutyric acid uptake. Over the concentrations of metformin that enhanced insulin action in H4IIE cells, the drug had no significant effect on insulin binding to its receptor. These studies suggest, therefore, that metformin may influence cellular metabolism by potentiating certain insulin actions through mechanisms that may be beyond insulin receptor binding.

Direct effects of biguanides on glucose utilization in vitro

The effect of the biguanides metformin and phenformin on glucose utilization in isolated cells was studied with IM-9 human lymphocytes. Both agents stimulated glucose consumption from the incubation media. Detectable effects of metformin were seen at 33 mumol/L and detectable effects of phenformin were seen at 1.7 mumol/L. Both agents, at similar concentrations, also stimulated [3H] 2-deoxy-D-glucose uptake. Studies with phenformin indicated that biguanides increase the Vmax of uptake without changing the Km. In contrast to the biguanides, IM-9 cells insulin did not influence either glucose consumption or [3H] 2-deoxy-D-glucose uptake. These data provide evidence, therefore, that biguanides may directly influence the cellular utilization of glucose.

Transient impairment of thyroid function in newborn from an area of endemic goiter

Thyroid function was studied in newborn from 3 areas of Sicily in which iodine intake is normal (area A), moderately decreased (area B), and severely decreased (area C). In the latter 2 areas, there is a high incidence of goiter and in area C endemic cretinism is present. TSH and T4 were measured in the cord serum of 5673 newborn from area A, 2096 from area B, and 184 from area C. The mean TSH value was significantly higher in areas C (P less than 0.001) and B (P less than 0.005) when compared to area A; moreover, in both endemic goiter areas the mean cord serum T4 was significantly reduced (P less than 0.01). All infants with cord serum TSH levels above 50 microU/ml were recalled because of the suspicion of congenital hypothyroidism. Such values were found in 41 of the 7953 infants (0.52%) with an increasing frequency from area A (9:5673 = 0.16%) to area B (14:2096 = 0.67%) to area C (18:184 = 9.78%). At the time of the recall examination [mean age, 32 +/- 8 (SD) days], 3 of the 41 recalled infants had died. Of the remaining 38 infants, 3 patterns evolved: 1) 23 had normal serum TSH and T4 values and were not studied further (false positives). 2) Eleven had elevated serum TSH and normal T4 values. They were reevaluated again after 3-6 weeks: all had normal values (transient hyperthyropinemia ). 3) Four infants had both high serum TSH and low serum T4 values (2 from area A and 2 from area C). They were diagnosed as having congenital hypothyroidism and treated with T4. At 10-13 months of age, after treatment withdrawal, the 2 infants from area A had permanent congenital hypothyroidism due to thyroid agenesis whereas the 2 infants from area C were euthyroid (transient congenital hypothyroidism). The present studies indicate, therefore, that in newborn from areas of iodine deficiency there is a higher frequency of elevated TSH levels and low T4 values than is found in areas where iodine intake is normal. This frequency is correlated to the degree of the iodine deficiency. The data suggest that the impairment of thyroid function at birth may be a transient phenomenon. The duration and the severity of the transient neonatal hypothyroidism, however, is greatly variable and its evolution unpredictable.

Effects of biguanides and sulfonylureas on insulin receptors in cultured cells

The effects of the two groups of oral agents on insulin receptors were studied in several types of cells in tissue culture: MCF-7 human breast cancer cells, IM-9 human lymphocytes, human fibroblasts, and H-35 rat hepatoma cells. In none of these cells did the four sulfonylureas tested, tolbutamide, glibenclamide (glyburide), gliclazide, and glisolamide, have any significant effects on insulin binding to its receptor. In contrast the two biguanides tested, phenformin and metformin, increased insulin binding in all cell types by 44 to 101%. These studies raise the possibility, therefore, that biguanides may have a direct effect on insulin receptors and this effect may account for the known effects of biguanides to lower elevated blood sugar levels in diabetic patients.

Insulin receptor antiserum and plant lectins mimic the direct effects of insulin on nuclear envelope phosphorylation

Insulin directly inhibits protein phosphorylation in isolated rat liver nuclear envelopes. In the present studies, an antiserum to insulin receptor as well as the plant lectins concanavalin A and phytohemagglutinin mimicked insulin action in isolated nuclear envelopes. These studies suggest that insulin and agents that mimic it may directly regulate nuclear functions.

Insulin regulation of protein phosphorylation in isolated rat liver nuclear envelopes: potential relationship to mRNA metabolism

The direct addition of insulin to highly purified nuclear envelopes prepared from the livers of diabetic rats resulted in a decrease in the incorporation of 32P into trichloroacetic acid-precipitable proteins. Autoradiography of 32P-labeled envelopes, solubilized in sodium dodecyl sulfate and subjected to electrophoresis, revealed that insulin decreased the phosphorylation of all major protein bands. Insulin produced detectable effects at concentrations between 0.1 and 1 pM, maximal effects at 10 pM, and progressively diminished effects at higher concentrations. Two insulin analogs, desdipeptide proinsulin and desoctapeptide insulin, had approximately 10% and 1%, respectively, the activity of native insulin. When nuclear envelopes were first phosphorylated with [gamma-32P]ATP and insulin was then added with an excess of unlabeled ATP, dephosphorylation was enhanced, suggesting that insulin was regulating nuclear envelope phosphatase activity. The direct addition of insulin to isolated rat liver nuclei in the presence of ATP stimulated the release of previously 14C-labeled trichloroacetic acid-precipitable mRNA-like material, and the direct addition of insulin to nuclear envelopes stimulated the activity of nucleoside triphosphatase, the enzyme that participates in mRNA nucleocytoplasmic transport. Moreover, the dose-response curves for these functions mirrored insulin's inhibition of nuclear envelope phosphorylation. These data suggest, therefore, a mechanism whereby insulin directly inhibits the phosphorylation of the nuclear envelope, leading in turn to the regulation of mRNA metabolism.

Phenformin has opposite effects on insulin and growth hormone binding to IM-9 lymphocytes

We studied simultaneously the effect of various concentrations of phenformin on insulin and growth hormone binding to IM-9 lymphocytes, a cell type known to have receptors for both these hormones. After 24 hr preincubation with phenformin at 2 x 10(-5) M, insulin binding to IM-9 cells was increased by 80.4 +/- 10.5% over control (mean +/- SE of 10 experiments). In parallel experiments HGH binding was decreased by 43.1 +/- 2.2% (mean +/- SE). This effect of phenformin was dose-dependent for both HGH and insulin binding over the concentration range 1.5 x 10(-6) M to 5 x 10(-5) M, and was already detectable 3 hr after phenformin addition. These data indicate that phenformin has an opposite effect on insulin and growth hormone binding to IM-9 cells. Several possible mechanisms might be suggested for the decrease of HGH binding sites induced by phenformin: the simultaneous opposite effect on HGH and insulin receptors raises the possibility that some metabolic event triggered by the drug is able to induce opposite changes in the binding of these two hormones with different biological activities.

Action of insulin at the nuclear envelope

Insulin binding sites are present on purified nuclear envelopes from liver and other tissues, and EM autoradiographs and other types of studies indicate that insulin can enter intact target cells and interact with several types of intracellular membranes, including the nuclear envelope. More recent studies indicate that insulin has direct effects on both mRNA efflux from isolated nuclei and nuclear envelope NTPase, the enzyme that regulates mRNA efflux. These studies raise the possibility, therefore, that insulin regulates mRNA levels in target cells by directly influencing nuclear membrane functions as NTPase. Since insulin does not dramatically elevate mRNA levels for all proteins, the question arises as to how insulin selectively increases mRNA for specific mRNAs. One possibility is that there is targeting of specific mRNA molecules for specific pore complexes and that insulin may only influence a certain fraction of the nuclear pores. Thus, continued investigation is needed concerning the role of polypeptide hormones such as insulin in nucleocytoplasmic exchange.

Effect of metformin on insulin binding to receptors in cultured human lymphocytes and cancer cells

The effect of the biguanide metformin (dimethyl-biguanide) on insulin binding in vitro to IM-9 lymphocytes and MCF-7 human breast cancer cells was studied. Metformin significantly increased insulin binding to both cell types: maximum increment was 47.1 +/- 7.0% greater than control in IM-9 and 38.0 +/- 6.1% in MCF-7 cells. The dose-response curves indicated that the latter cell line was more sensitive to metformin, with a significant effect apparent at a metformin concentration of 7.7 x 10(-6) mol/l, similar to the levels reached in patients treated with this drug. When compared with phenformin, metformin was less active in increasing insulin binding to cultured cells, the ratio between the two drug responses being similar to that of their therapeutic dosage in patients. Insulin binding increment due to metformin was reversible, was not dependent on new protein synthesis and was evident also in IM-9 lymphocytes that had been down-regulated by pre-incubation with insulin (10(-7) mol/l). This effect of metformin on insulin binding to receptors may contribute to the hypoglycaemic effect of this agent in patients.

Insulin stimulation of nucleoside triphosphatase activity in isolated nuclear envelopes

The activity of nucleoside triphosphatase, an enzyme that regulates nuclear messenger RNA transport, was measured in highly purified nuclear envelopes isolated from rat liver. Addition of picomolar concentrations of insulin to freshly prepared nuclear envelopes directly increased the enzyme activity. The major effect of insulin on this enzyme was to increase the maximum velocity of its activity; no significant effects were seen on the affinity constant. These studies raise the possibility, therefore, that the nuclear envelope is a site where insulin regulates nuclear functions.

Insulin binding sites on the nuclear envelope: potential relationship to mRNA metabolism

Insulin regulates the growth and metabolism of most tissues. The hormonal potency of insulin results, to a large extent, from its ability to regulate target cells at a variety of subcellular sites. For many years, the effects of insulin on membrane transport, enzyme activity, and protein synthesis have been studied extensively. Less attention, however, was given to how insulin regulates nuclear functions. Recently the presence of specific binding sites for insulin on nuclei and nuclear envelopes have been documented and characterized. These binding sites have biochemical characteristics that are different from insulin binding sites on the plasma membrane. Moreover, direct in vitro effects of insulin on messenger RNA (mRNA) metabolism have recently been reported. These effects include the stimulation of mRNA efflux from intact nuclei, and stimulation of nucleoside triphosphatase activity (NTPase), the enzyme that regulates mRNA efflux. Thus, significant insight is now being gained concerning the action of insulin on the cell nucleus.

High incidence of anti-GH antibodies in subjects treated with the GH clinical preparation available in Italy

We have characterized the GH clinical preparation available in Italy (Grorm, Serono) by gel chromatography and immunoreactivity. Only 50-60% of this preparation can be identified with the active GH monomeric form. Both higher and lower molecular weight compounds are present as well. Then, using a radioimmunoassay technique, we looked for anti-GH antibodies in 21 subjects under Grorm treatment and found them in 6 paitents (28.6%). Two subjects having anti-GH antibodies with high affinity had a lower growth rate. These data suggest that anti-GH antibodies measurement is clinically useful in patients treated with this GH preparation. A more purified preparation should be used when a slowing down of the growth rate is observed in the presence of anti-GH antibodies.