Fibrolamellar carcinoma of the liver with a mixture of ordinary hepatocellular carcinoma: a case report

Fibrolamellar carcinoma (FLC) of the liver is a rare variant of hepatocellular carcinoma (HCC), and only 13 cases have been reported in Japan up to 1997. We described a histologically unusual case of FLC. A 52-yr-old man was admitted to our hospital for work-up of hepatic mass. Laboratory examinations revealed no abnormalities except elevated serum alpha-fetoprotein (AFP) (2098 ng/ml). A diagnosis of HCC was made by imaging findings, and left lobectomy of the liver was performed. Histologically, the tumor was composed of areas of FLC mixed with ordinary HCC and those of pure ordinary HCC. Staining for AFP was positive in the HCC component and negative in the FLC component. Some cases of such mixed tumors have been reported in Europe and the United States, but not in Japan. We regarded our case as the first of the mixed tumor in Japan.

Ineffective use of a detachable snare for colonoscopic polypectomy of large polyps

BACKGROUND

Colonoscopic polypectomy of large polyps may be associated with complications such as bleeding. Use of a detachable snare may reduce the risk of bleeding. We describe several instances in which the use of such a device proved to be ineffective.

METHODS

A detachable snare was used for colonoscopic polypectomy of large polyps in 18 patients (20 polyps), also applied at the residual stalk after conventional polypectomy in 5 patients (5 polyps), and evaluated retrospectively.

RESULTS

Sixteen of the 20 polyps were pedunculated, and 4 were semi-pedunculated. In 3 of the 4 semi-pedunculated lesions, the loop slipped off after polypectomy because the lesions were cut close to the site of encirclement. Bleeding occurred in 4 cases because of transection by the loop of a thin stalk (4 mm) before polypectomy (1), slipping of the loop in a semi-pedunculated lesion (1), or insufficient tightening of the loop (2). After conventional polypectomy, we could not effectively snare the residual stalk because of flattening in 3 of the 5 lesions.

CONCLUSIONS

Use of the detachable snare for polypectomy of thin stalked or semi-pedunculated lesions may result in technical failure of this technique. The stalk should be fully encircled with the snare before polypectomy. The detachable snare is difficult to apply at the residual stalk after conventional polypectomy.

Calcified pseudoaneurysm of the left ventricle

Left ventricular pseudoaneurysm following acute myocardial infarction generally has an extremely poor prognosis without surgical repair. A rare case of long term survival for 23 years following cardiac rupture with subsequent development of a left ventricular pseudoaneurysm after acute myocardial infarction is reported. The patient suffered acute inferoposterior myocardial infarction in July 1974 at the age of 58 years. Clinical course and findings obtained on reassessment in 1992 (transesophageal echocardiography, chest computed tomography and left ventriculography) confirmed a left ventricular pseudoaneurysm. The patient refused surgical resection of the lesion, but remained alive and well in 1997 (81 years old). In this case, it is considered that containment of hemorrhage by pericardial adhesion prevented immediate tamponade and sudden death.

Simultaneous activation of signals through gp130, c-kit, and interleukin-3 receptor promotes a trilineage blood cell production in the absence of terminally acting lineage-specific factors

We assessed the biologic role of signaling through gp130, a signal-transducing receptor (R) component, in human hematopoiesis in vitro. Although peripheral blood-derived CD34(+) cells ubiquitously expressed gp130 and interleukin-3 receptor alpha (IL-3Ralpha), IL-6Ralpha was only detected on 80% of these CD34(+) cells. We sorted CD34(+)IL-6R+ or CD34(+)IL-6R- cells and studied the effect on hematopoietic colony formation of signaling through gp130 activated by IL-6 or a combination of IL-6 and recombinant soluble human IL-6R (sIL-6R) in the presence or absence of stem cell factor (SCF ) and/or IL-3. Signals activated by SCF, IL-6, or IL-6/sIL-6R complex alone did not induce significant colony formation. However, a combination of IL-3, SCF, and IL-6/sIL-6R complex dramatically induced many neutrophil (colony-forming unit-granulocyte [CFU-G]), erythroid burst (burst-forming unit-erythrocyte [BFU-E]), erythrocyte-containing mixed (CFU-Mix), and megakaryocyte (CFU-Meg) colony formations when CD34(+)IL-6R- cells were used as the target. CFU-G colony formation induced by the three signals was more evident when CD34(+)IL-6R+ cells were used as the target. This distinct synergistic effect of the three different signals was confirmed by single-cell clone-sorting experiments. Moreover, colony formation (including CFU-G, BFU-E, CFU-Mix, and CFU-Meg) was observed even in the presence of neutralizing antibodies for granulocyte colony-stimulating factor, erythropoietin, and thrombopoietin (c-Mpl), whereas neutralizing antibodies for gp130, IL-6R, IL-3, and SCF partially or completely blocked the synergistic effect. The maturation of neutrophilic, erythroid, and megakaryocytic cells supported by the three signals in serum-free cultures was confirmed by immunostaining using anti-CD66b, antiglycophorin A, antihemoglobin alpha, and anti-CD41 monoclonal antibodies, respectively. In contrast, any two of the three signals were insufficient for effective blood cell production in the absence of maturation factors. These results suggest that simultaneous activation of the three signals through gp130, c-kit, and IL-3R can induce in vitro proliferation and differentiation of trilineage hematopoietic progenitors in the absence of terminally acting lineage-specific factors.

An increase in peripheral blood progenitor cells in primates by coadministration of recombinant human interleukin 6 and recombinant human granulocyte colony-stimulating factor

BACKGROUND

We recently demonstrated that coadministration of recombinant human interleukin 6 (rhIL-6) and recombinant human granulocyte colony-stimulating factor (rhG-CSF) in mice synergistically increases peripheral blood stem cells (PBSC), which can rescue lethally irradiated recipient mice. However, there is little information about the effect of coadministration of rhIL-6 and rhG-CSF on PBSC in a primate system.

METHODS

In cynomolgus monkeys, rhG-CSF (5 microg/kg day) alone was administered for 5 days (first cycle). After the wash-out period, rhIL-6 (0, 10, or 20 microg/kg/day) and rhG-CSF were coadministered for 5 days (second cycle).

RESULTS

Total peripheral colony-forming cells levels were increased earlier by coadministration of rhIL-6 and rhG-CSF than by the administration of rhG-CSF alone. The maximum level in the coadministration cycle was obtained on day 5, and a high level was obtained for a further 3 days after cessation. The maximum number of peripheral total colony-forming cells in the coadministration cycle was a mean of 2.12-fold (range 1.38 to 3.35) higher than that in the rhG-CSF alone cycle. Coadministration also increased the peripheral mixed colony-forming units by a mean of 3.62-fold (range 1.02 to 5.52). Interestingly, monkeys that showed a low response to the administration of rhG-CSF alone also had a higher response to the coadministration. No significant difference was observed between the two cycles of administration of rhG-CSF alone.

CONCLUSIONS

These findings suggest that coadministration of rhIL-6 and rhG-CSF may be useful for clinical PBSC collection.

Negative strand of hepatitis C virus RNA in the liver of patients with chronic hepatitis C after interferon treatment

In patients receiving interferon therapy for chronic hepatitis C, serum hepatitis C virus (HCV) RNA often reverts from an undetectable to a detectable form after completion of treatment. Detection of the negative strand of HCV-RNA in liver tissue is regarded as an index of viral proliferation. Therefore, we investigated changes in the hepatic negative-strand HCV-RNA following interferon therapy to determine whether this parameter could predict the long-term response to treatment. The subjects of this study were 27 patients with chronic active hepatitis C. Serum positive-strand and hepatic tissue negative-strand HCV-RNA were detected using polymerase chain reaction. At the completion of interferon treatment, serum HCV-RNA was not detected in 21 patients. One year following treatment it remained undetectable in 14 of these patients but it had reverted to a detectable form in seven. The 14 patients in whom hepatic negative-strand RNA was not detected between 2 weeks and 12 months after treatment, had not relapsed after another year. In the 13 remaining patients, negative-strand RNA was found in liver tissue and serum RNA either reverted to a detectable form or remained detectable throughout. From these findings, we conclude that the detection of negative-strand HCV-RNA in liver tissue 2 weeks after the completion of interferon therapy is useful for predicting the long-term effect of therapy.

Effect of b-mercaptoethanol on the viability of IVM/IVF/IVC bovine embryos during long-distance transportation in plastic straws

Experiments were conducted to assess the effect of beta-mercaptoethanol (beta-ME) on the quality and viability of bovine blastocysts derived from in-vitro culture (IVC) of in-vitro matured and fertilized (TVM-IVF) oocytes during their transport between 2 distant places. Follicular oocytes were collected from ovaries obtained at a slaughterhouse and were cultured for 20 to 21 h in modified TCM-199. The IVM oocytes were fertilized in vitro with frozen-thawed spermatozoa. Fertilized oocytes were cultured for 7 d, and embryos that developed to the blastocyst stage were used for the experiments. The blastocysts, packed in straws with transportation medium that consisted of modified TCM-199 with HEPES equilibrated in air and supplemented with 20 % calf serum and 0, 10, 50, 100 or 150 microM beta-ME, were transported at 37 degrees C from Tokyo to Sapporo by air (18.3 h). The quality of blastocysts was assessed and ranked as excellent (A), good (B), fair (C) or poor (D) after transportation. The percentages of blastocysts ranked as A or B were significantly higher (P < 0.05) when the embryos were transported in beta-ME supplemented medium (80 to 100%) than when transported without beta-ME (54 %). Blastocysts ranked as A or B after transportation in medium with or without 150 microM beta-ME were nonsurgically transferred to synchronous recipients; 60 d after embryo transfer, 21/36 and 19/35 cows, respectively, were diagnosed as pregnant by palpation per rectum. These results indicate that beta-ME maintains the quality of bovine blastocysts in plastic straws for several hours without control of CO2 and that the concentration of beta-ME used in this experiment is not detrimental to the blastocysts.

Interleukin-6 and granulocyte colony-stimulating factor synergistically increase peripheral blood progenitor cells in myelosuppressive mice

We previously reported a successful peripheral blood stem cell harvest by co-administration of recombinant human (rh) interleukin-6 (IL-6) and rh granulocyte colony-stimulating factor (G-CSF) in normal mice. In the present study, to evaluate further the utility of this observation for autologous peripheral blood stem cell transplantation, we examined the effects of rhIL-6 and rhG-CSF on peripheral blood granulocyte-macrophage colony-forming units (CFU-GM) in carboplatin (CBDCA)-induced and irradiation-induced myelosuppressive mouse models. After CBDCA administration, blood cell counts decreased to the nadir, and then recovered to a normal level. In this recovery phase, the peripheral CFU-GM level increased to 3.8-fold higher than the pretreatment level. Administration of rhIL-6 (10 microgram/day) alone induced a 40-fold increase in peripheral CFU-GM from the normal level at day 14. In combination with rhG-CSF (0.35 microgram/day), which alone induced a 74-fold increase, rhIL-6 synergistically increased the CFU-GM level by 1200-fold. In irradiated mice, similar results were observed. Administration of rhIL-6 at 3 and 10 microgram/day significantly increased CFU-GM. Interestingly, in combination with rhG-CSF, a lower dose of rhIL-6 (1 microg/day) could induce CFU-GM increase. We also examined CFU-GM distribution in bone marrow, spleen and peripheral blood. Cytokine administration induced not only a change of CFU-GM distribution, but also an increase in total CFU-GM counts per mouse. These results suggest that co-administration of rhIL-6 and rhG-CSF may be useful for autologous peripheral blood stem cell transplantation.

Coadministration of interleukin-6 (IL-6) and soluble IL-6 receptor delays progression of wobbler mouse motor neuron disease

Interleukin-6 (IL-6), a multipotential cytokine, initiates signal transduction pathways similar to those of ciliary neurotrophic factor (CNTF) and leukemia inhibitory factor (LIF). These molecules share the signal transducing receptor component, gp130. IL-6 triggers homodimerization of gp130, whereas CNTF and LIF induce heterodimerization of gp130 and LIF receptor. Although CNTF or LIF treatment attenuates motor deficits in wobbler mouse motor neuron disease (MND), neuroprotective effects of IL-6 on this animal have not yet been clarified. Here we studied whether simultaneous treatment with IL-6 and soluble IL-6 receptor (sIL-6R) can ameliorate symptomatic and neuropathological changes in wobbler mouse MND. After clinical diagnosis at postnatal age 3-4 weeks, wobbler mice received subcutaneous injection with human recombinant IL-6 (1.0 mg/kg), human sIL-6R (0.5 mg/kg), IL-6 + sIL-6R or vehicle, daily for 4 weeks in a blind fashion. Compared to vehicle, coadministration with IL-6 and sIL-6R potentiated grip strength, attenuated muscle contractures in the forelimbs, reduced denervation muscle atrophy and prevented degeneration of spinal motor neurons. Single administration with IL-6 or sIL-6R did not retard the symptomatic and neuropathological progression, although IL-6-treated mice did not raise anti-IL-6 antibodies. Treatment with IL-6 + sIL-6R, but not with IL-6 or sIL-6R alone delayed progression of wobbler mouse MND. Our results indicate that the neuroprotective mechanism for IL-6/sIL-6R on wobbler mouse MND differs from that of CNTF or LIF alone. We hypothesize that IL-6/sIL-6R complex may function on motor neurons through activation and homodimerization of gp130.

[AP-PCR and AP-PCR-SSCP analyses]

DNA fingerprinting by arbitrarily primed polymerase chain reaction (AP-PCR) is a simple and informative method to investigate genetic changes in cancers. The discovery of a mutator phenotype in hereditary non-polypotic colon cancer by the AP-PCR fingerprinting demonstrated the usefulness of this unbiased method. Due to its semiquantitative amplification of the target DNA, the AP-PCR fingerprinting can be applied to analyze numerical changes of chromosome fragments. A recent breakthrough of the chromosomal assignment of human AP-PCR products enabled us to do PCR-mediated molecular karyotyping of cancers. Application of single-strand conformation polymorphism (SSCP) analysis to AP-PCR products seems to be promising to elucidate somatic point mutations and hidden losses of heterozygosity in the anonymous regions in cancers.

A novel aspect of the maturational step of megakaryocytes in thrombopoiesis: bundle formation of microtubules in megakaryocytes

We demonstrated bundle formation of microtubules both in the cytoplasmic processes and in the cytoplasm near the nucleus of cultured megakaryocytes by means of electron and immunofluorescent microscopy. To determine whether this bundle formation was related to megakaryocyte maturation, we studied the effects of recombinant human interleukin-6 (rhIL-6) in vitro and in vivo on this event. About 75% of the megakaryocytes in the bone marrow had no fibrous microtubule structures in the cytoplasm (type I), and about 25% had bundles of microtubules (type II). The formation of these bundles was promoted by rhIL-6 both in vitro and in vivo. Considerably more megakaryocytes cultured with recombinant murine (rm) IL-3 and rhIL-6 became type II than those cultured with rmIL-3 alone. Megakaryocytes from mice given rhIL-6 (10 microg/animal/d) subcutaneously also began to form bundles in proportion to an increase in platelet counts. After the administration of rhIL-6, about half of the megakaryocytes contained microtubule bundles in their cytoplasm. These results indicate that microtubule-bundle formation is one maturational event in megakaryocyte development and that rhIL-6 could accelerate this event.

Histopathological assessment of lymph node metastasis in patients with gastric cancer

BACKGROUND/AIMS

Lymph node dissection has been carried out for two decades in Japan, resulting in improved survival of patients with gastric cancer. By analyzing dissected nodes of resected advanced gastric cancers, we intend to determine which parameter(s) are more concerned in node metastasis.

PATIENTS AND METHODS

Curative gastrectomy with dissection of lymph nodes was performed for 78 of the 108 patients with advanced gastric cancer. Metastases were found in 171 of 1359 nodes (13%) dissected. In each node, the maximum and minimum diameters were measured, and the ratio of the former to the latter was calculated.

RESULTS

The minimum diameter of node was closely related to node metastasis. When the minimum diameter in node metastatic criteria was "3 mm or more", a sensitivity of 81% and specificity of 54% were calculated. In false negative node, signet-ring cell carcinoma (SIG) (33%) and poorly differentiated adenocarcinoma (POR) (22%) were more frequently found as primary lesions. Half or more of these nodes were invaded by only a few carcinoma cells. When the primary lesion is histologically SIG or POR, endoscopic treatment is contraindicated for possible nodes metastasis.

CONCLUSIONS

It is impossible to distinguish nodes with micrometastasis from nodes without metastasis. The minimum diameter of node is more important in node metastasis of gastric cancer than the maximum diameter of node or the ratio of both.

Association between p34cdc2 levels and meiotic arrest in pig oocytes during early growth

The molecules involved in determining meiotic competence were determined in porcine oocytes isolated from preantral and antral follicles of different sizes. Oocytes isolated from preantral follicles had a mean diameter of 78 microns, contained diffuse filamentous chromatin in the germinal vesicle and were incapable of progressing from the G2 to the M phase of the cycle even after 72 h in culture. Oocytes from early antral follicles had a mean diameter of 105 microns, showed a filamentous chromatin configuration and about half resumed meiosis but arrested at metaphase I (MI) when cultured. Oocytes from mid-antral (3-4 mm) and large antral follicles (5-6 mm) had mean oocyte diameters of 115 and 119 microns respectively, contained condensed chromatin around the nucleolus and progressed to metaphase II (MII) in 48% and 93% of instances respectively. Analysis of p34cdc2, the catalytic subunit of maturation promoting factor (MPF), by immunoblotting indicates that the inability of small (78 microns) oocytes to resume meiosis is due, at least in part, to inadequate levels of the catalytic subunit of MPF. On the other hand, the inability of intermediate-sized (105 microns) oocytes from antral follicles to complete the first meiotic division by progressing beyond MI appears not to be limited by levels of p34cdc2, which are maximal by this stage. We postulate that an inadequacy of molecules other than p34cdc2 limits progression of MI to MII; the acquisition of these molecules during the final stages of growth may be correlated with the formation of the perinucleolar chromatin rim in the germinal vesicle.

Establishment and characterization of a new human mesothelioma cell line (T-85) from malignant peritoneal mesothelioma with remarkable thrombocytosis

A mesothelioma cell line, termed T-85, was established from a patient with malignant peritoneal mesothelioma and remarkable thrombocytosis (1.4 x 10(6)/mm3). Electron microscopically, two types of mesothelioma cells have been characterized; the major type of cells with dense-cored granules in the cytoplasm and the minor one with evenly dense granules. Immunologically, the cells showed staining for interleukin-6 (IL-6), cytokeratin, collagen type IV, vimentin, laminin, fibronectin and Factor VIII-related antigen. Quantitation by ELISA revealed a high concentration of IL-6 in T-85 cell culture supernatants. RT-polymerase chain reaction of T-85 cells showed two positive bands of cDNA at 628 and 251 base pairs indicating the constitutive expression of IL-6 and IL-6 receptor mRNA. Moreover, prominent pro-platelet process formation activity in T-85 cell culture supernatants indicated the presence of a thrombopoietic activity due mainly to IL-6 but not the c-Mpl ligand or erythropoietin. However, the fact that 15% of PPF activity remained in the supernatants treated with anti-IL-6 antibody indicated the presence of another thrombopoietic substance. T-85 is so far the first mesothelioma cell line derived from a case with remarkable thrombocytosis.

Focal nodular hyperplasia of the liver without central scar

An unusual case of focal nodular hyperplasia (FNH) of the liver is presented. A 31-year-old male was admitted to our hospital for the evaluation of an hepatic mass 10 cm in diameter located in segment 4. Routine examinations including liver function tests were all normal. Hepatitis B surface antigen, hepatitis C virus antibody, alpha-fetoprotein were all negative. Imagining studies could not detect specific findings of FNH such as a central scar structure or a spoke-wheel appearance due to dilated tumor vessels coursing centrally followed by radiating peripheral coursing vessels. Extensive left lobectomy of the liver was performed. Histological examination of the specimen cut into 1-cm-thick slices revealed no central stellate scars. Preoperative diagnosis of FNH with imaging studies was difficult because of the absence of central scars.

A synergistic increase in transplantable peripheral blood stem cells in mice by co-administration of recombinant human interleukin 6 and recombinant human granulocyte colony-stimulating factor

We examined the effects of co-administration of recombinant human (rh) IL-6 (10 micrograms/day) and rh granulocyte colony-stimulating factor (G-CSF) (0.35 micrograms/day) on the number of peripheral blood cells and peripheral progenitor cells in mice. Among blood cells counts, only white blood cells were synergistically enhanced by co-administration of rhIL-6 and rhG-CSF. Moreover, it was found that co-administration of rhIL-6 and rhG-CSF also caused a marked synergistic increase in the number of peripheral blood progenitor cells. Namely, in combination with rhG-CSF, which alone induced a 170-fold increase in peripheral granulocyte-macrophage colony-forming units (CFU-GM) on day 14, rhIL-6 synergistically increased the number of CFU-GM to more than 1600-fold higher than the number in control mice. Administration of rhIL-6 alone induced a 46-fold increase in CFU-GM. Similar synergistic increases of other hematopoietic progenitors, such as colony-forming units in spleen and megakaryocyte colony-forming units in blood, were also observed in mice co-administered rhIL-6 and rhG-CSF. The survival rate of lethally irradiated recipient mice transplanted with mononuclear cells from 100 microliters of blood from mice administered rhIL-6 and/or rhG-CSF was examined. When mononuclear cells from mice co-administered rhIL-6 and rhG-CSF were injected, survival rate at day 100 was 92%. In contrast, recipient mice transplanted with mononuclear cells from mice administered either rhIL-6 or rhG-CSF alone showed a survival rate of 31% or 46%, respectively, although transplantation of mononuclear cells from control mice failed to rescue any lethally irradiated recipient mice. These results suggest that co-administration of rhIL-6 and rhG-CSF may be useful for peripheral blood stem cell transplantation.

Apoptosis as a mechanism of skin renewal: Le(y)-antigen expression is involved in an early event of a cell's commitment to apoptosis

Skin renewal is a typical example of the active participation of a cell in its own death process. Cells arising from mitotic activity in the stratum germinativum of the epidermis continuously migrate upwards to the stratum corneum, where dead cells are eventually desquamated. Recent studies have suggested that apoptosis is involved in the dynamic process of skin renewal. However, this still remains to be further elucidated. In this paper, we investigated the involvement of apoptosis in the skin renewal process. Changes in the morphology of cells in different epidermal layers were compared with histochemical analyses of the extent of DNA fragmentation, as determined by nick end-labelling, and of the reactivities to a monoclonal antibody directed to Le(y)-antigen, difucosylated type 2 chain determinant, which has a close association with apoptosis, and to a monoclonal antibody directed to the proliferating cell nuclear antigen. The results show that apoptosis proceeds concomitantly with cell movement in the epidermis. It seems likely that commitment of a cell to death by apoptosis occurs in the epidermal tissue immediately after completion of cell proliferation, and that Le(y)-antigen expression may be involved in the entire apoptotic process including this early event.

Effects of prostaglandins and oestradiol-17 beta on oxytocin binding in cultured bovine luteal cells

The aim of the investigation was to evaluate the possible action of prostaglandins (PGs) and oestradiol-17 beta (oestradiol) on the specific binding for oxytocin in bovine luteal cells. Cultured cells of bovine corpora lutea at the mid-luteal stage (Day 8-12 of the oestrous cycle) were examined for the presence of oxytocin receptors by a radioreceptor assay using the 125I-labelled oxytocin antagonist [d(CH2)5,Tyr(Me)2,Thr4,Tyr-NH29]-vasotocin (125I-OVT) as a ligand. The cells were cultured for 48 h in total. In the final 15 h of culture, the luteal cells were exposed to varying concentrations of PGF2 alpha, PGE2 and/or oestradiol. After culture, the cells were incubated with 37,000 dpm (0.5 nM) 125I-OVT with or without 100 nM of unlabelled oxytocin. PGF2 alpha, at 10(-8) M and 10(-7) M, stimulated the specific binding for oxytocin to levels as high as 128% of controls (P < 0.01); by contrast, PGE2, PGI2 or oestradiol had no effect on oxytocin binding. Scatchard analysis revealed that the concentration of oxytocin receptors was increased (P < 0.05) from 6.7 fmol micrograms-1 DNA to 8.4 fmol micrograms-1 DNA by stimulation with 10(-7) M of PGF2 alpha without changing the binding affinity. No further increase in the specific binding was observed when PGF2 alpha was used in combination with PGE2, PGI2 or oestradiol at a concentration of 10(-7) M. Addition of indomethacin (28 microM) resulted in the inhibition of PGF2 alpha secretion, coinciding with a significant decrease in oxytocin binding (P < 0.01). However, addition of arachidonic acid (100 microM) caused a significant increase in the secretion of PGF2 alpha and the specific binding for oxytocin concomitantly (P < 0.05). When the protein kinase C (PKC) activity of the luteal cells was inactivated by preincubating cells for 13 h with 1 microM phorbol 12-myristate 13-acetate before PGF2 alpha stimulation, the specific binding for oxytocin was not affected by PGF2 alpha stimulation (10(-7) M) in the final 15 h of culture. These data suggest that PGF2 alpha may be one of the potent regulators for luteal oxytocin receptors in a paracrine and/or autocrine manner, and that its action is mediated by PKC.