A phase I/II study of cancer peptide vaccine S-288310 in patients with advanced urothelial carcinoma of the bladder.

Background: S-288310, a cancer peptide vaccine composed of two HLA-A*24:02-restricted peptides derived from two oncoantigens, DEP domain-containing 1 (DEPDC1) and M-phase phosphoprotein 1 (MPHOSPH1), was investigated in urothelial carcinoma (UC) of the bladder. Patients and methods: Thirty eight HLA-A*24:02-positive patients with progressive UC were enrolled in this study. In the phase I part of the study, three patients each were treated with S-288310 at 1 mg or 2 mg/peptide subcutaneously once a week to evaluate safety and tolerability. In the phase II, 32 patients were randomized to receive either 1 mg or 2 mg to evaluate the difference in cytotoxic T lymphocytes (CTL) induction and safety. Results: S-288310 was safe and well tolerated in the phase I. Of 27 patients evaluable for immune responses in the phase II, there was no difference in CTL induction rate between the 1 mg (100%) and 2 mg (80.0%) groups. Of 32 patients receiving S-288310 in the phase II, the most frequent drug-related AE was the injection site reaction that was observed in 29 patients (90.6%), but none of the patients discontinued administration due to these reactions and no dose relationship in the frequency and severity was observed. The objective response rate of the 32 patients was 6.3% and the disease control rate was 56.3%. The median overall survival (OS) rates for patients vaccinated with S-288310 after one regimen of chemotherapy, 2 regimens, or 3 or more were 14.4, 9.1 and 3.7 months, respectively, and 32.2% of patients post first-line treatment were alive at 2 years. OS of patients who showed CTL induction to both peptides was longer than that of those with CTL induction to no or one peptide. Conclusion: S-288310 was well-tolerated and effectively induced peptide-specific CTLs, which were correlated with longer survival for patients with UC of the bladder. Trial registration ID: JapicCTI-090980.

Regulation of gene expression in prostate cancer cells with an artificially constructed promoter responsive to radiation.

A promoter library was developed that is composed of DNA fragments constructed by randomly elongating the cis-acting elements of transcription factors presumably activated in prostate cancer by radiation, and linking to the TATA-box sequence. One promoter with the strongest reactivity to X-ray in the LNCap cells of the library was chosen and improved by the introduction of random mutations. The resultant promoter was designated clone 880-8, showing the highest dose-dependent activity enhancement with X-ray irradiation (X-irradiation). A recombinant retrovirus expressing the luciferase gene under the control of clone 880-8 was infected into LNCap cells that showed 9.12±0.36-fold enhancement of luciferase activity 12 h after X-irradiation at 10 Gy. When the infected cells were inoculated onto nude mice, enhancement of luciferase expression was 4.27±1.36-fold 12 h after X-irradiation at 10 Gy. When LNCap was infected with another recombinant carrying the fcy::fur gene downstream from clone 880-8, fcy::fur expression was enhanced by X-irradiation. It was also shown to increase the dose-dependent cell killing ratio with 5-FC as compared with a counterpart without X-irradiation. These results suggest that the method used in this study is effective to construct a promoter responsive to stimulation. Such promoters can be used for stimulation-controlled gene therapies.

Selective interaction of vitamin D receptor with transcriptional coactivators by a vitamin D analog.

The nuclear vitamin D receptor (VDR) is a member of a nuclear receptor superfamily and acts as a ligand-dependent transcription factor. A family of cotranscriptional activators (SRC-1, TIF2, and AIB-1) interacts with and activates the transactivation function of nuclear receptors in a ligand-dependent way. We examined interaction of VDR with these coactivators that was induced by several vitamin D analogs, since they exert differential subsets of the biological action of vitamin D through unknown mechanisms. Unlike other vitamin D analogs tested, OCT (22-oxa-1alpha,25-dihydroxyvitamin D3) induced interaction of VDR with TIF2 but not with SRC-1 or AIB-1. Consistent with these interactions, only TIF2 was able to potentiate the transactivation function of VDR bound to OCT. Thus, the present findings suggest that the structure of VDR is altered in a vitamin D analog-specific way, resulting in selective interactions of VDR with coactivators. Such selective interaction of coactivators with VDR may specify the array of biological actions of a vitamin D analog like OCT, possibly through activating a particular set of target gene promoters.

Characterization of transactivational property and coactivator mediation of rat mineralocorticoid receptor activation function-1 (AF-1).

The autonomous activation function-2 (AF-2) in the mineralocorticoid receptor (MR) E/F domain is known to play a major role in the ligand-induced transactivation function of MR; however, it remained unclear about the transactivation function of its A/B domain. We therefore tried to characterize the MR A/B domain as the AF-1 and further studied the actions of known coactivators for AF-2 in the E/F ligand-binding domain in the function of the MR A/B domain. Deletion analyses of rat and human MRs revealed that the A/B domains harbor a transactivation function acting as AF-1. The MR mutant (E959Q) with a point mutation in helix 12, which causes a complete loss of MR AF-2 activity, still retained ligand-induced transactivation function, indicating a significant role for AF-1 in the full activity of the ligand-induced MR function. Among the coactivators tested to potentiate the MR AF-2, TIF2 and p300 potentiated the MR AF-1 through two different core regions [amino acids (a.a.) 1-169, a.a. 451-603] and exhibited functional interactions with the MR A/B domain in the cultured cells. However, such interactions were undetectable in a yeast and in an in vitro glutathione-S-transferase pull-down assay, indicating that the functional interaction of TIF2 and p300 with the MR A/B domain to support the MR AF-1 activity require some unknown nuclear factor(s) or a proper modification of the A/B domain in the cells.

Inhibition of bone resorption by pamidronate cannot restore normal gain in cortical bone mass and strength in tail-suspended rapidly growing rats.

To clarify how the changes in bone formation and resorption affect bone volume and strength after mechanical unloading, the effect of inhibition of bone resorption by a potent bisphosphonate, pamidronate, on bone mineral density (BMD), histology, and strength of hind limb bones was examined using tail-suspended growing rats. Tail suspension for 14 days reduced the gain in the BMD of the femur at both the metaphysis rich in trabecular bone and the diaphysis rich in cortical bone. Treatment with pamidronate increased the total BMD as well as that of the metaphysis of the femur but had almost no effect on the BMD of the diaphysis in both control and tail-suspended rats. Histological examinations revealed that 14-day tail suspension caused a loss of secondary cancellous bone with a reduction in the trabecular number and thickness in comparison with control rats. In the femoral diaphysis, the diameter and cortical bone thickness increased to a lesser degree in tail-suspended rats when compared with rats without tail suspension, and a marked reduction in bone formation and the layers of alkaline phosphatase-positive cells was observed at the periosteal side. Pamidronate treatment increased secondary cancellous bone but could not restore normal growth-induced periosteal bone apposition and bone strength. Because the material strength of the femoral diaphysis at the tissue level was not affected by pamidronate treatment, the inability of pamidronate to prevent the reduction in physical strength of the femoral diaphysis does not appear to be due to a change in the quality of newly formed bone. These results demonstrate that tail suspension reduces the growth-induced periosteal modelling drift and that the antiresorptive agent pamidronate is unable to restore normal periosteal bone apposition.

A new synthetic steroid, osaterone acetate (TZP-4238), increases cortical bone mass and strength by enhancing bone formation in ovariectomized rats.

A new synthetic steroid, 17 alpha-acetoxy-chloro-2-oxa-4,6-pregnadiene-3,20-dione (osaterone acetate, TZP-4238), has a potent antiandrogenic and gestagenic action with virtually no estrogenic and androgenic activity in their classical target organs. In the present study, the effects of TZP-4238 on the structure, strength, and turnover of the rat long bones were examined. Female Wistar rats at 12 weeks of age were ovariectomized (OVX) and treated with TZP-4238 or 17 beta-estradiol (E2) every day for 12 weeks. TZP-4238 significantly increased the diameters and maintained bone mineral density (BMD) of the femur of OVX rats. Although the BMD of the total femur was higher in E2-treated rats than that in TZP-treated rats, E2 did not increase the diameters of the femurs. To examine the effects of TZP-4238 and E2 on the BMD of different regions of the femur, the BMD was further analyzed by dividing it into 20 regions of equal longitudinal length. E2 increased the BMD of the distal and proximal metaphysis, regions rich in trabecular bone, but had no effect on the BMD of the femoral diaphysis compared with OVX control rats. In contrast, 2.5 and 12.5 mg/kg TZP-4238 increased the BMD of the femoral diaphysis, regions rich in cortical bone, but did not affect the BMD at the distal metaphysis. In agreement with the changes in the BMD of different regions of the femur, TZP-4238 but not E2 increased the physical strength of the femoral diaphysis assessed by a three-point bending test. Histomorphometric analyses of the cross-sections of the tibia revealed that TZP-4238 increased but E2 reduced the periosteal bone formation rate compared with OVX rats. In addition, TZP-4238 caused an increase in serum bone alkaline phosphatase with only a mild and transient decrease in urinary deoxypyridinoline excretion, while E2 reduced both of these parameters. These results demonstrate that TZP-4238 increases the dimension, BMD, and physical strength of the rat long bones by enhancing cortical bone formation, while estrogen maintains trabecular BMD by inhibiting bone resorption. Because the physical strength of long bones is affected by cortical bone mass and geometry, the effect of TZP-4238 on cortical bone may have a potential for the treatment of osteoporosis with reduced cortical bone formation.

A new compound heterozygous mutation in the 11 beta-hydroxysteroid dehydrogenase type 2 gene in a case of apparent mineralocorticoid excess.

Apparent mineralocorticoid excess (AME) characterized by early-onset hypertension and hypokalemia is due to congenital deficiency of 11 beta-hydroxysteroid dehydrogenase (11 beta HSD). Two isoforms of human 11 beta HSD are known, and the type 2 isoform (11 beta HSD2) has been recently shown to be responsible for AME. In this study we have analyzed the 11 beta HSD2 gene of a Japanese patient with AME. PCR amplification and subsequent nucleotide sequencing of the 11 beta HSD2 gene from the patient and his family members revealed that the patient has a compound heterozygous mutation of this gene. In 1 allele, an undescribed single nucleotide transition in codon 208 in exon 3 resulted in a substitution of arginine to histidine (CGC to CAC: R208H). In the other allele, a deletion of 3 nucleotides in codons 337-338 in exon 5 resulted in a substitution of arginine to histidine and a deletion of tyrosine residue (CGCTAT to CAT: R337H, delta Y338), which has been previously shown to abolish 11 beta HSD2 enzyme activity. A chloramphenicol acetyltransferase assay-based expression study involving the mineralocorticoid receptor indicated that the novel R208H mutation eliminates the enzymatic activity of 11 beta HSD2. From the genetic analysis of 50 healthy subjects, the novel R208H mutation was unlikely to be due to polymorphism. Together, these results indicate that this patient is a compound heterozygote for the mutation in the 11 beta HSD2 gene (R208H and R337H, delta Y338) and that these mutations inactivate the 11 beta HSD2 function and give rise to clinically manifest AME.

Effect of mechanical unloading and reloading on periosteal bone formation and gene expression in tail-suspended rapidly growing rats.

In order to delineate the influence of mechanical unloading on the formation and resorption of trabecular and cortical bone, the effects of mechanical unloading on the volume, structure, and turnover of hindlimbs were examined using tail-suspended rapidly growing rats. In addition, to clarify the mechanism of how mechanical stimulation affects bone formation, the influence of reloading on the messenger ribonucleic acid (mRNA) expression of genes related to differentiation or proliferation of bone cells was examined. Tail suspension of 5-week-old rats for 14 days caused a suppression of the increase in the diameter, subperiosteal area, and bone mineral density (BMD) of the femur. The suppression of the increase in femoral BMD was composed of an early impairment in the gain of BMD at the femoral metaphysis, which is rich in trabecular bone, and a sustained reduction in the gain of BMD at the femoral diaphysis, which is rich in cortical bone. The early reduction in the increase of BMD at the metaphysis was due to an enhancement of bone resorption, whereas a sustained reduction of periosteal bone formation appeared to play an important role in the suppression of gain in cortical bone mass and size by mechanical unloading. Mechanical reloading of the hind limbs after 14 days of tail suspension caused a transient increase within 2 h of the expression of cyclooxygenase (COX)-2 in intraosseous cells, composed mainly of osteocytes, and in the expression of c-fos in periosteal cells. However, because the COX-2 expression in osteocytes was not enhanced after 20 min of reloading when the c-fos expression was already increased in periosteal cells, the enhancement of c-fos expression does not appear to be mediated by an increased production of prostaglandins in the osteocytes. It is suggested that mechanical unloading causes an impairment of periosteal bone formation by impairing the expression of c-fos in periosteal cells. The intercellular signaling cascade that mediates the enhancement of c-fos expression in periosteal cells in response to mechanical stimulation remains to be elucidated.

Effect of prostatic neuropeptides on invasion and migration of PC-3 prostate cancer cells.

We investigated the effect of various neuropeptides present in the prostate, including calcitonin gene-related peptide (CGRP), gastrin-releasing peptide (GRP), substance P (SP), neuropeptide Y (NPY), vasoactive intestinal polypeptide (VIP), calcitonin (CT), leucine-enkephalin (L-ENK), glucagon and parathyroid hormone-related protein (PTH-rP), on the invasion of PC-3 prostate cancer cells through a reconstituted basement membrane (Matrigel) using a Transwell cell culture chamber assay. Both CGRP and GRP increased the invasive capacity of tumor cells, whereas SP inhibited it. On the other hand, VIP, CT, L-ENK, NPY, glucagon and PTH-rP had no significant effect. Both CGRP and GRP also increased the haptotactic migration of tumor cells to fibronectin, but SP inhibited it. These three neuropeptides had no effect on either adhesion to fibronectin and laminin or on the gelatinolytic activities of MMP-9 in gelatin zymography, nor did they affect the growth of tumor cells at concentrations used in this study. These results indicate that both GRP and CGRP increased the invasive potential of PC-3 cells probably through enhancement of cell motility, while SP inhibited the invasiveness through suppression of motile response.

Expression of membrane-type 1 matrix metalloproteinase (MT1-MMP) on prostate cancer cell lines.

Membrane-type metalloproteinase-1 (MT1-MMP) is a transmembrane metalloproteinase, which activates proMMP-2 and expressed on the cell surface in many invasive cancer cells. We investigated the expression of MT1-MMP in prostate cancer cell lines. MT1-MMP protein and mRNA were expressed in PC-3, DU-145 and TSU-pr1 cells (androgen-independent prostate cancer cell lines), but in LNCaP cells (androgen-dependent prostate cancer cell line). MT1-MMP protein was negative and mRNA was low to detect by RT-PCR. Cell lysate of PC-3 cleaved proMMP-2 to the active form. In addition, both hepatocyte growth factor (HGF) and gastrin-releasing peptide (GRP) increased Matrigel invasion and induced the expression of MT1-MMP protein in DU-145 prostate cancer cells. These results suggest that MT1-MMP is indeed the tumor-specific activator of proMMP-2 in androgen-independent prostate cancer cells and plays an important role in the invasive properties of prostate cancer cells.

Effect of chromogranin A (pancreastatin) fragment on invasion of prostate cancer cells.

We investigated the effect of chromogranin A (pancreastatin) fragment on the invasion of PC-3, DU-145 and LNCaP prostate cancer cells through a reconstituted basement membrane (Matrigel) using a Transwell cell culture chamber assay. Chromogranin A fragment increased the invasive capacity of both PC-3 and DU- 145 cells, whereas it had no significant effect of LNCaP cells. Chromogranin A fragment also increased the haptotactic migration of both PC-3 and DU-145 cells to fibronectin. Furthermore chromogranin A fragment increased the fibrinolytic activities of urokinase-type plasminogen activator (u-PA) in fibrin zymograms of both PC-3 and DU-145 cells and the expression of u-PA mRNA of PC-3 cells. However, the growth of these tumor cells was not affected by chromogranin A fragment at any concentrations used in this study. These results indicate that chromogranin A fragment increased the invasive potential of both PC-3 and DU-145 cells probably through enhancement of cell motility and the production of u-PA.

A novel angiogenic inhibitor derived from Japanese shark cartilage (I). Extraction and estimation of inhibitory activities toward tumor and embryonic angiogenesis.

Guanidine extraction and crude fractionation of Japanese shark cartilage by ultrafiltration on a molecular weight basis were conducted and the antiangiogenic activities were assayed as to the inhibitions of tumor and embryonic angiogenesis. Significant inhibition of angiogenesis was found, and there was a linear relationship between the results of the two assays. The inhibitory activities were concentrated in the fraction in the molecular weight range of 103 to 104, and were resistant to heat treatment.

Angiogenic activity of rat mammary carcinomas induced by 7,12-dimethylbenz[a]anthracene and its inhibition by medroxyprogesterone acetate: possible involvement of antiangiogenic action of medroxyprogesterone acetate in its tumor growth inhibition.

The significant inhibitory activity of medroxyprogesterone acetate (MPA) against mammary tumors induced by 7,12-dimethylbenz[a]anthracene (DMBA) was confirmed in female Sprague-Dawley (SD) rats, and was found to be independent of the estrogen receptor (ER) level. To facilitate elucidation of the mechanism underlying the antitumor activity of MPA against the rat mammary tumors (RMTs) regardless of ER status, the present study was conducted to determine whether or not a DMBA-induced RMT had the capacity to elicit angiogenic activity on tissue implantation into a rabbit cornea, and, if so, to determine whether or not the angiogenic activity of the RMT was inhibited by MPA. The RMTs obtained were classified into two groups based on the ER level; ER-positive and -negative groups. Both groups exhibited relatively strong angiogenic activity, the activity of the ER-negative group being significantly higher than that of the ER-positive one. The angiogenesis produced by both groups of RMTs was significantly inhibited by MPA, as judged from the results of the rabbit cornea assay. Similarly, MPA almost entirely suppressed not only the angiogenesis but also the growth of rabbit VX2 tumors without ER, included as a positive control as to the induction of angiogenic activity. In vitro experiments using neoplastic epithelioid RMT-1 and -2 cells cloned from DMBA-induced RMTs demonstrated that MPA had little or no suppressive effect on the growth of these epithelial cells. These results suggest that the inhibitory action of MPA toward the angiogenic activity of RMTs, at least in part, involves its antitumor activity toward the RMTs.

Klinefelter's syndrome with prepenile scrotum.

Two cases of Klinefelter's syndrome with prepenile scrotum were presented. They underwent the operation for prepenile scrotum according to Glenn and Anderson's method. Thereafter urethroplasty was performed in each case. The decrease in response to testosterone in the target organ was noticed in 1 patient, suggesting that some androgen resistance in this case was attributable in part to anomaly of genitalia.

Internal spermatic vein prostaglandins in varicocele patients.

Blood was collected from 20 patients with varicocele (15 in the infertile group and 5 in the incidental varicocele group) at the time of high ligation by insertion of a catheter into the internal spermatic vein toward the renal side. Simultaneously, blood was obtained from the antecubital vein. The levels of cortisol, prostaglandin (PG)(A + B), PGE, and PGF in these blood samples were measured. Although no differences in cortisol and PG(A + B) levels were observed between internal spermatic and peripheral vein bloods in varicocele patients examined, PGE and PGF levels were higher in internal spermatic venous bloods than in peripheral venous bloods. Differences in PGF levels between the samples of blood from the internal spermatic vein and from the peripheral vein in cases of the infertile group were larger than those of the incidental varicocele group. PGE and PGF in internal spermatic vein blood samples were correlated. The possibility that PGE and PGF, refluxed from the renal vein to the testes via the internal spermatic vein in varicocele patients, disturbs spermatogenesis is discussed.

Induction of urokinase-type plasminogen activator by lipopolysaccharide in PC-3 human prostatic cancer cells.

Urokinase-type plasminogen activator (uPA) plays a central role in many aspects of cellular regulation, such as fibrinolysis, cell migration, and metastasis. The uPA induction by inflammatory stimuli such as IL-1, TNFalpha, and lipopolysaccharide (LPS) has been reported in a number of human cells. We examined the effects of LPS on uPA expression in human PC-3 prostatic cancer cells that express uPA in a conditioned medium. LPS increased the uPA accumulation in PC-3 cells, whereas IL-1, IL-6, and TNFalpha did not. Northern blot analysis revealed that the peak induction of uPA mRNA occurred 5 hours after LPS stimulation. A protein synthesis inhibitor, cycloheximide, amplified the LPS-induced uPA mRNA, suggesting that LPS induces uPA by activating the gene expression in which de novo protein synthesis is not necessary.

Serum soluble Fas level for detection and staging of prostate cancer.

To evaluate the clinical usefulness of measuring serum soluble Fas (sFas) for differentiation between prostate cancer and benign prostate hyperplasia (BPH) and for staging of prostate cancer, serum sFas and PSA were determined in 38 and 20 men with prostate cancer and BPH, respectively, before treatment. In 17 patients, sFas and PSA were measured one hour after transrectal ultrasound-guided sextant biopsy in order to examine the leakage of sFas into the circulation after prostatic injury. Patients with prostate cancer had a significantly higher level of sFas than those with BPH. The serum sFas level was statistically elevated in patients with metastatic prostate cancer. There was a statistically significant correlation between sFas and PSA in patients with prostate cancer but not in those without cancer. The serum sFas did not change one hour after systematic prostatic biopsy although PSA levels were markedly elevated. sFas levels might be useful as a discriminator between prostate cancer and BPH while sFas might indicate the tumor burden in patients with prostate cancer.

Effect of a matrix metalloproteinase inhibitor (ONO-4817) on lung metastasis of murine renal cell carcinoma.

We examined the anti-metastatic effect of a newly developed inhibitor of synthetic matrix metalloproteinase (MMP), ONO-4817, on experimental pulmonary metastasis of murine renal cell carcinoma (Renca) cells and on tumor cell invasion, through reconstituted basement membrane (Matrigel) in vitro using the same cells. Oral administration of ONO-4817 (50-200 mg/kg/day) to Renca-bearing mice resulted in a dose-dependent inhibition of lung metastasis without a loss of body weight. ONO-4817 at the high dose of 200 mg/kg showed a tendency to prolong the survival of the mice. We also found that oral administration of ONO-4817 significantly inhibited the angiogenic response (number of vessels oriented towards the tumor mass) and the growth of tumors inoculated i.d. in syngeneic mice. In addition, ONO-4817, at non-cytotoxic concentrations of less than 10 microM, caused a marked inhibition of the invasion of Renca cells as compared to the vehicle control. Gelatin zymography revealed that ONO-4817 inhibited the enzymatic activity of MMP-2 produced by Renca cells in a concentration-dependent manner. In conclusion, ONO-4817 effectively inhibited lung metastasis of Renca cells through its anti-invasive and anti-angiogenic properties. These results suggest that use of the MMP inhibitor (MMPI) ONO-481 7 may provide a therapeutic basis for preventing lung recurrence and metastasis of renal cell carcinoma.

Effect of interferon-alpha A/D in combination with the Japanese and Chinese traditional herbal medicine juzen-taiho-to on lung metastasis of murine renal cell carcinoma.

Several studies have shown that the Kampo medicine Juzen-taiho-to (Si-Quan-Da-Bu-Tang in Chinese) has various biological activities, including anti-tumor effects when combined with surgical excision or with chemotherapeutic drugs. Here we investigated the effect of combined therapy with interferon (IFN)-alpha A/D and Juzen-taiho-to on experimental lung metastasis of murine renal cell carcinoma (Renca) cells. Five consecutive administrations of IFN-alpha A/D to Renca-bearing mice resulted in dose-dependent inhibition of lung metastasis. IFN-alpha A/D at the dose of 100,000 IU/mouse significantly inhibited the metastasis, but a marked loss of body weight was observed during and after the administration. In contrast, oral administration of Juzen-taiho-to (50 mg/mouse) alone tended to inhibit the metastasis, but the effect was not statistically significant. The combination treatment of suboptimal doses of IFN-alpha A/D and Juzen-taiho-to markedly augmented the antimetastatic effect without causing any loss of body weight, as compared with either treatment alone. Similar results were also obtained by treatment with IFN-gamma in combination with Juzen-taiho-to. Clinically, immunotherapy with IFNs has been primarily approved for the treatment of patients with metastatic renal cell carcinoma, but sufficient efficacy has not yet been obtained. Therefore, the combination of IFNs with Juzen-taiho-to may provide a means to increase the therapeutic potential of IFNs and to decrease their toxicity for the treatment of metastatic renal cell carcinoma.

Effects of heat exposure on plasma insulin, glucagon and metabolites in response to nutrient injection in heifers.

Effects of heat exposure on plasma insulin, glucagon, and metabolite responses following injection of various nutrients were investigated in heifers. Four heifers, fed hay wafer and a commercial concentrate, were exposed to thermoneutral (20 degrees C) and hot (30 degrees C) environments. Glucose, arginine and butyrate (each injection at 0.625 mmol/kg) and insulin (0.2 U/kg) were injected intravenously, and then blood samples were collected at regular intervals through jugular vein catheters. Insulin secretion in response to glucose and arginine injection was not affected by heat exposure. However, the insulin response following butyrate injection was inhibited in heifers exposed to heat. In the hot environment, glucagon responses following the arginine and butyrate injections were augmented significantly, however glucagon levels were inhibited following the glucose injection. It is concluded that heat stress causes an inhibition of the insulin response to butyrate injection, and an increase in the glucagon response following arginine and butyrate injection. Plasma metabolite concentrations altered in accordance with the changes in the concentration of pancreatic hormones.