The incorporation of cystine by the soluble carrier family 7 member 11 (SLC7A11) is a component of the redox regulatory mechanism in stallion spermatozoa†

Oxidative stress is considered a major mechanism causing sperm damage during cryopreservation and storage, and underlies male factor infertility. Currently, oxidative stress is no longer believed to be caused only by the overproduction of reactive oxygen species, but rather by the deregulation of redox signaling and control mechanisms. With this concept in mind, here, we describe for the first time the presence of the soluble carrier family 7 member 11 (SLC7A11) antiporter, which exchanges extracellular cystine (Cyss) for intracellular glutamate, in stallion spermatozoa, as well as its impact on sperm function using the specific inhibitor sulfasalazine. Spermatozoa incubated with Cyss exhibited an increased intracellular GSH content compared with controls (P < 0.01): 50% in fresh extended stallion spermatozoa and 30% in frozen-thawed spermatozoa. This effect was prevented by the addition of sulfasalazine to the media. Cystine supplementation also reduced the oxidation-reduction potential of spermatozoa, with sulfasalazine only preventing this effect on fresh spermatozoa that were incubated for 3 h at 37°C, but not in frozen-thawed spermatozoa. While sulfasalazine reduced the motility of frozen-thawed spermatozoa, it increased motility in fresh samples. The present findings provide new and relevant data on the mechanism regulating the redox status of spermatozoa and suggest that a different redox regulatory mechanism exists in cryopreserved spermatozoa, thus providing new clues to improve current cryopreservation technologies and treat male factor infertility.

Phosphorylated AKT preserves stallion sperm viability and motility by inhibiting caspases 3 and 7

AKT, also referred to as protein kinase B (PKB or RAC), plays a critical role in controlling cell survival and apoptosis. To gain insights into the mechanisms regulating sperm survival after ejaculation, the role of AKT was investigated in stallion spermatozoa using a specific inhibitor and a phosphoflow approach. Stallion spermatozoa were washed and incubated in Biggers–Whitten–Whittingham medium, supplemented with 1% polyvinyl alcohol (PVA) in the presence of 0 (vehicle), 10, 20 or 30 μM SH5, an AKT inhibitor. SH5 treatment reduced the percentage of sperm displaying AKT phosphorylation, with inhibition reaching a maximum after 1 h of incubation. This decrease in phosphorylation was attributable to either dephosphorylation or suppression of the active phosphorylation pathway. Stallion spermatozoa spontaneously dephosphorylated during in vitro incubation, resulting in a lack of a difference in AKT phosphorylation between the SH5-treated sperm and the control after 4 h of incubation. AKT inhibition decreased the proportion of motile spermatozoa (total and progressive) and the sperm velocity. Similarly, AKT inhibition reduced membrane integrity, leading to increased membrane permeability and reduced the mitochondrial membrane potential concomitantly with activation of caspases 3 and 7. However, the percentage of spermatozoa exhibiting oxidative stress, the production of mitochondrial superoxide radicals, DNA oxidation and DNA fragmentation were not affected by AKT inhibition. It is concluded that AKT maintains the membrane integrity of ejaculated stallion spermatozoa, presumably by inhibiting caspases 3 and 7, which prevents the progression of spermatozoa to an incomplete form of apoptosis.

Free Spanish abstract

A Spanish translation of this abstract is freely available at http://www.reproduction-online.org/content/148/2/221/suppl/DC1.

Caspase activation, hydrogen peroxide production and Akt dephosphorylation occur during stallion sperm senescence

To investigate the mechanisms inducing sperm death after ejaculation, stallion ejaculates were incubated in BWW media during 6 h at 37°C. At the beginning of the incubation period and after 1, 2, 4 and 6 h sperm motility and kinematics (CASA), mitochondrial membrane potential and membrane permeability and integrity were evaluated (flow cytometry). Also, at the same time intervals, active caspase 3, hydrogen peroxide, superoxide anion (flow cytometry) and Akt phosphorylation (flow cytometry) were evaluated. Major decreases in sperm function occurred after 6 h of incubation, although after 1 h decrease in the percentages of motile and progressive motile sperm occurred. The decrease observed in sperm functionality after 6 h of incubation was accompanied by a significant increase in the production of hydrogen peroxide and the greatest increase in caspase 3 activity. Additionally, the percentage of phosphorylated Akt reached a minimum after 6 h of incubation. These results provide evidences that sperm death during in vitro incubation is largely an apoptotic phenomena, probably stimulated by endogenous production of hydrogen peroxide and the lack of prosurvival factors maintaining Akt in a phosphorylated status. Disclosing molecular mechanisms leading to sperm death may help to develop new strategies for stallion sperm conservation.

During cooled storage the extender influences processed autophagy marker light chain 3 (LC3B) of stallion spermatozoa

To investigate the role of the processed autophagy marker light chain 3 (LC3B) protein in sperm survival in stallion semen processing during cooled storage, split ejaculates were diluted in two different extenders, KMT and INRA 96, and LC3B processing and sperm quality evaluated during incubation at 5°C for five days. After 3 days of incubation there was a drop in total motility in both extenders, although the percentage of progressive motile sperm was greater (P<0.05) in samples extended in INRA96. On Day 5 of cooled storage all sperm parameters decreased significantly independent of the extender, however, samples extended in INRA 96 maintained motility values while those extended in KMT had a further decrease in motility compared with data collected on Day 3 of incubation. The percentage of live sperm decreased over the time of incubation, but only in samples incubated in KMT. The extender had a marked effect in LC3B processing during cooled storage. Spermatozoa maintained in KMT extender did not exhibit LC3B processing, while in spermatozoa incubated in INRA96 there was an increase (P<0.01) in LC3B processing after 5 days of cooled storage. Stallion spermatozoa experience LC3B turnover during cooled storage, however, the extent depends on the extender used. Apparently LC3B turnover is associated with enhanced survival.

Sex sorting increases the permeability of the membrane of stallion spermatozoa

At present, the only repeatable means of selecting the sex of offspring is the Beltsville semen sorting technology using flow cytometry (FC). This technology has reached commercial status in the bovine industry and substantial advances have occurred recently in swine and ovine species. In the equine species, however, the technology is not as well developed. To better understand the changes induced in stallion spermatozoa during the sorting procedure, pooled sperm samples were sorted: sperm motility and kinematics were assessed using computer assisted sperm analysis, sperm membrane integrity was assessed using the YoPro-1 assay, while plasmalemmal stability and lipid architecture were assessed using Merocyanine 540/SYTOX green and Annexin-V, respectively. Lipid peroxidation was also investigated with the probe Bodipy(581/591)-C11. All assays were performed shortly after collection, after incubation and after sex sorting using FC. In order to characterize potential molecular mechanisms implicated in sperm damage, an apoptosis protein antibody dot plot array analysis was performed before and after sorting. While the percentage of total motile sperm remained unchanged, sex sorting reduced the percentages of progressive motile spermatozoa and of rapid spermatozoa as well as curvilinear velocity (VCL). Sperm membranes responded to sorting with an increase in the percentage of YoPro-1 positive cells, suggesting the sorted spermatozoa had a reduced energy status that was confirmed by measuring intracellular ATP content.

Differential glycolytic and glycogenogenic transduction pathways in male and female bovine embryos produced in vitro

Previous studies have shown that developmental kinetic rates following IVF are lower in female than in male blastocysts and that this may be related to differences in glucose metabolism. In addition, an inhibition of phosphatidylinositol 3-kinase (PI3-K) inhibits glucose uptake in murine blastocysts. Therefore, the aim of this study was to identify and compare the expression of proteins involved in glucose metabolism (hexokinase-I, HK-I; phosphofructokinase-1, PFK-1; pyruvate kinase 1/2, PK1/2; glyceraldehyde-3-phosphate dehydrogenase, GAPDH; glucose transporter-1, GLUT-1; and glycogen synthase kinase-3, GSK-3) in male and female bovine blastocysts to determine whether PI3-K has a role in the regulation of the expression of these proteins. Hexokinase-I, PFK-1, PK1/2, GAPDH and GLUT-1 were present in bovine embryos. Protein expression of these proteins and GSK-3 was significantly higher in male compared with female blastocysts. Inhibition of PI3-K with LY294002 significantly decreased the expression of HK-I, PFK-1, GAPDH, GSK-3A/B and GLUT-1. Results showed that the expression of glycolytic proteins HK-I, PFK-1, GAPDH and PK1/2, and the transporters GLUT-1 and GSK-3 is regulated by PI3-K in bovine blastocysts. Moreover, the differential protein expression observed between male and female blastocysts might explain the faster developmental kinetics seen in males, as the expression of main proteins involved in glycolysis and glycogenogenesis was significantly higher in male than female bovine embryos and also could explain the sensitivity of male embryos to a high concentration of glucose, as a positive correlation between GLUT-1 expression and glucose uptake in embryos has been demonstrated.

Autophagy and apoptosis have a role in the survival or death of stallion spermatozoa during conservation in refrigeration

Apoptosis has been recognized as a cause of sperm death during cryopreservation and a cause of infertility in humans, however there is no data on its role in sperm death during conservation in refrigeration; autophagy has not been described to date in mature sperm. We investigated the role of apoptosis and autophagy during cooled storage of stallion spermatozoa. Samples from seven stallions were split; half of the ejaculate was processed by single layer centrifugation, while the other half was extended unprocessed, and stored at 5°C for five days. During the time of storage, sperm motility (CASA, daily) and membrane integrity (flow cytometry, daily) were evaluated. Apoptosis was evaluated on days 1, 3 and 5 (active caspase 3, increase in membrane permeability, phosphatidylserine translocation and mitochondrial membrane potential) using flow cytometry. Furthermore, LC3B processing was investigated by western blotting at the beginning and at the end of the period of storage. The decrease in sperm quality over the period of storage was to a large extent due to apoptosis; single layer centrifugation selected non-apoptotic spermatozoa, but there were no differences in sperm motility between selected and unselected sperm. A high percentage of spermatozoa showed active caspase 3 upon ejaculation, and during the period of storage there was an increase of apoptotic spermatozoa but no changes in the percentage of live sperm, revealed by the SYBR-14/PI assay, were observed. LC3B was differentially processed in sperm after single layer centrifugation compared with native sperm. In processed sperm more LC3B-II was present than in non-processed samples; furthermore, in non-processed sperm there was an increase in LC3B-II after five days of cooled storage. These results indicate that apoptosis plays a major role in the sperm death during storage in refrigeration and that autophagy plays a role in the survival of spermatozoa representing a new pro-survival mechanism in spermatozoa not previously described.

Dissecting the molecular damage to stallion spermatozoa: the way to improve current cryopreservation protocols?

We review recent developments in the technology of freezing stallion sperm, paying special attention to the molecular lesions that spermatozoa suffer during freezing and thawing, such as osmotic stress, oxidative damage, and apoptotic changes. We also discuss the applicability of colloidal centrifugation in stallion sperm cryobiology. Increased knowledge about the molecular injuries that occur during cryopreservation may lead to improved protective techniques and thus to further improvements in fertility in the current decade.

Identification and regulation of glycogen synthase kinase-3 during bovine embryo development

The aim of this study was to examine the presence and regulation of glycogen synthase kinase-3alpha (GSK3A) and GSK-3beta (GSK3B) in bovine embryos and their possible roles in embryo development. Our results show that GSK3A and GSK3B are present in bovine embryos at the two-cell stage to the hatched blastocyst stage. Bovine embryo development was associated with an increase in the phosphorylation of both isoforms, being statistically significant at blastocyst and hatched blastocyst stages, compared with earlier stages. Inhibition of GSK3 with CT99021 (3 microM) resulted in a significant increase in the percentage and quality of blastocysts, while inhibition of GSK3 with lithium chloride (LiCl; 20 mM) significantly reduced at the proportion of eight-cell embryos on day 3 and inhibited blastocyst formation. The use of LY294002 (10 microM), a specific inhibitor of phosphatidylinositol-3 kinase, also produced a significant decrease in embryo development. In addition, treatment with LiCl and LY294002 produced a significant decrease in the serine phosphorylation of both isoforms of GSK3. Finally, CT99021 and LiCl reduced the phosphorylation of beta-catenin on Ser45 in two-cell embryos, while LY294002 increased it. Despite the fact that LiCl inhibited GSK3 activity, as demonstrated by beta-catenin phosphorylation, its effects on the bovine embryo could be mediated through other signaling pathways leading finally to a decrease in the phosphorylation of GSK3 and a reduction in embryo development. Therefore, in conclusion, GSK3A/B serine phosphorylation was positively correlated with embryo development, indicating the importance of an accurate regulation of GSK3 activity during developmental stages to achieve normal bovine embryo development.

Morphometry of porcine spermatozoa and its functional significance in relation with the motility parameters in fresh semen

Both the study and the relationship between sperm design and sperm function have been a target of several researchers. In our study we have evaluated the relationship between the morphometry of sperm head and midpiece as well as the relationship between morphometry of these two spermatic components and sperm motion characteristics in the boar. Analysis of regression (lineal and multiple) and principal components analysis were used for the study of these relationships. Semen samples from five Iberian boars were taken for analysis. Analysis of morphometry was assessed by CASMA system and motility by CASA system. Sperm midpiece showed a significant relationship (positive or negative, depending on the morphometric parameter evaluated) with sperm head. VSL, LIN, STR, BCF and VAP showed a significant relationship with several head and midpiece morphometric parameters. Finally, through the analysis of multiple lineal regression we obtained several statistical models that predict STR, LIN, VCL, ALH, BCF, PC1 and PC2 (the last two variables have been obtained from a principal components analysis) as a function of one, two or three morphometric parameters. Our results suggest a co-evolution of sperm head and midpiece and in addition that sperm motion characteristics of porcine spermatozoa are influenced by morphometry of head and midpiece.

Porcine sperm motility is regulated by serine phosphorylation of the glycogen synthase kinase-3alpha

Sperm functions are critically controlled through the phosphorylation state of specific proteins. Glycogen synthase kinase-3 (GSK3) is a serine/threonine kinase with two different isoforms (alpha and beta), the enzyme activity of which is inhibited by serine phosphorylation. Recent studies suggest that GSK3 is involved in the control of bovine sperm motility. Our aim was to investigate whether GSK3 is present in porcine spermatozoa and its role in the function of these cells. This work shows that both isoforms of GSK3 are present in whole cell lysates of porcine sperm and are phosphorylated on serine in spermatozoa stimulated with the cAMP analog, 8Br-cAMP. A parallel increase in serine phosphorylation of the isoform GSK3alpha, but not in the isoform GSK3beta, is observed after treatments that also induce a significant increase in porcine sperm velocity parameters. Therefore, a significant positive correlation among straight-line velocity, circular velocity, average velocity, rapid-speed spermatozoa, and GSK3alpha serine phosphorylation levels exists. Inhibition of GSK3 activity by alsterpaullone leads to a significant increase in the percentage of rapid- and medium-speed spermatozoa as well as in all sperm velocity parameters and coefficients. Moreover, pretreatment of porcine spermatozoa with alsterpaullone significantly increased the percentage of capacitated porcine spermatozoa and presents no effect in the number of acrosome-reacted porcine spermatozoa. Our work suggests that the isoform GSK3alpha plays a negative role in the regulation of porcine sperm motility and points out the possibility that sperm motile quality might be modulated according the activity state of GSK3alpha.

Phosphatidylinositol 3-kinase pathway regulates sperm viability but not capacitation on boar spermatozoa

Phosphatidylinositol 3-kinase (PI3-K) plays an important role in cell survival in somatic cells and recent data pointed out a role for this kinase in sperm capacitation and acrosome reaction (AR). This study was undertaken to evaluate the role of PI3-K pathway on porcine spermatozoa capacitation, AR, and viability using two unrelated PI3-K inhibitors, LY294002 and wortmannin. In boar spermatozoa, we have identified the presence of PDK1, PKB/Akt, and PTEN, three of the main key components of the PI3-K pathway. Incubation of boar sperm in a capacitating medium (TCM) caused a significant increase in the percentage of capacitated (25 +/- 2 to 34 +/- 1% P < 0.05, n = 6) and acrosome reacted (1 +/- 1 to 11 +/- 1% P < 0.01, n = 6) spermatozoa compared with sperm in basal medium (TBM). Inhibition of PI3-K did affect neither the capacitation status nor AR nor protein p32 tyrosine phosphorylation of boar spermatozoa incubated in TBM or TCM. Boar sperm viability in TBM was significantly decreased by 40 and 20% after pretreatment with LY294002 or wortmannin, respectively. Similar results were observed after incubation of boar spermatozoa in TCM. Treatment of boar spermatozoa with the analog of cAMP, 8Br-cAMP significantly prevented the reduction on sperm viability. Our results provide evidence for an important role of the PI3-K pathway in the regulation of boar sperm viability and suggests that other signaling pathways different from PI3-K must be activated downstream of cAMP to contribute to regulation of sperm viability. Finally, in our conditions the PI3-K pathway seems not related with boar sperm capacitation or AR.

Morphometric changes in boar spermatozoa induced by cryopreservation

Computer-assisted sperm morphometry analysis was used to determine the effects of cryopreservation on boar sperm head and midpiece morphometry. Sperm-rich fractions were collected from five mature boars. Three microscope slides were prepared from single extended sperm samples prior freezing and post-thawing. All slides were stained with Hemacolor, and 250 sperm images were obtained from each slide. The sperm head dimensions for length, width, area, perimeter and four shape factors and sperm-midpiece dimensions for area, width, angle and distance were determined in each spermatozoa. The effects of sperm freezing on sperm dimensions within and among boars were determined. A previous discriminant analysis of the results was able to correctly classify a 78.3 and 82% of fresh and frozen-thawed spermatozoa respectively. Sperm heads were significantly smaller in cryopreserved spermatozoa than in the companion extended samples for length, width, area and perimeter. Sperm midpieces were also significantly smaller in cryopreserved spermatozoa for width and area. The highest changes in morphometric dimensions after the freeze-thawing process were found in the midpiece of spermatozoa. The variability of morphometric measurements only was significantly different between fresh and thawed samples for head rugosity and midpiece area. The effects of cryopreservation on morphometric parameters were similar in the boars, which allow us to conclude that cryopreservation process does not have a different effect in each individual boar. In summary, morphometric changes associated with the cryopreservation process on boar spermatozoa do not apparently depends on an effect at individual level.

Standardization of sample preparation, staining and sampling methods for automated sperm head morphometry analysis of boar spermatozoa

The accuracy of computer-assisted sperm morphometry analysis (CASMA) depends on the careful preparation, fixation and staining of spermatozoa. The efficiency of CASMA may be enhanced by developing optimized protocols. The aim of the present study was to evaluate the influence of sperm washing and the use of three staining techniques [rapid Panoptic, Hemacolor and Harris's Haematoxylin (HH)] on image-processing accuracy and boar sperm head morphometry. Sperm washing had a significant effect on samples stained with rapid Panoptic, increasing the percentage of correctly binarized sperm heads and the contrast between cells and background. However, rapid Panoptic yielded the lowest percentage of properly digitized sperm heads. HH provided the highest cell/background contrast, and also greater sperm head staining intensity, but discrimination of sperm midpieces was considered insufficient. Hemacolor occupied an intermediate position, providing acceptable colour intensity and satisfactory cell/background contrast. Use of different staining procedures prompted dimensional differences in sperm head morphometry. Significant differences between animals were observed for all morphometric parameters. Low within-animal variation coefficients reflected a homogeneous sperm head population. Between-animal variation coefficients were relatively high for Hemacolor and HH, and significantly high for the rapid Panoptic stain. Using Panoptic and HH, stable morphometric measurements required at least 100 properly digitized sperm heads rather than 200, while Hemacolor required only 50 spermatozoa. These results indicate that both washing of semen and staining procedures significantly affect the accuracy of image processing and sperm head dimensions. Hemacolor and HH proved to be the best staining techniques for evaluating sperm head dimensions in boar.

Changes in tyrosine phosphorylation associated with true capacitation and capacitation-like state in boar spermatozoa

Capacitation is defined as a series of events that render boar sperm competent to fertilize, either in vivo or in vitro. Moreover, preliminary stages of cryopreservation of spermatozoa involving cooling to 5 degrees C have been shown to induce capacitation-like changes in boar spermatozoa. Capacitation of boar spermatozoa is accompanied by protein phosphorylation, however the relationship between both processes is poorly understood. Capacitation status was assessed by chlortetracycline (CTC) staining. Changes in protein tyrosine phosphorylation were examined in pre-cleared whole cell lysates using a specific anti-phosphotyrosine monoclonal antibody. Our results in boar spermatozoa show a significant positive correlation between p32 tyrosine phosphorylation levels and percentage of capacitated (CTC pattern B) spermatozoa. Moreover, incubation of boar spermatozoa with two unrelated tyrosine kinase inhibitors induces a significant reduction in the percentages of capacitated and acrosome-reacted (AR) boar spermatozoa and a reduction in the p32 tyrosine phosphorylation. In our conditions, cooling boar spermatozoa to 5 degrees C and rewarming to 39 degrees C in a noncapacitating medium results in similar CTC staining patterns to those obtained after incubation of boar sperm for 1 or 4 hr at 39 degrees C in a capacitating medium. However, cooled-rewarmed fails to induce an increase in p32 tyrosine phosphorylation in boar spermatozoa. Moreover, CTC staining patterns of cooled-rewarmed spermatozoa do not change after incubation with a tyrosine kinase inhibitor. In conclusion, our results show a direct relationship between capacitation and tyrosine phosphorylation and suggest that p32 tyrosine phosphorylation levels could be used as a marker of the true capacitation changes observed in boar spermatozoa. Moreover, our results show that true capacitation and capacitation-like changes induced after cooling involve alternative intracellular tyrosine phosphorylation pathways in boar spermatozoa.

Inhibition of phosphatidylinositol 3-kinase modifies boar sperm motion parameters

Motility is the most widely used indicator of sperm quality. Besides modulation by the cAMP pathway little is known regarding the intracellular pathways that regulate boar sperm motility. Recently the role of phosphatidylinositol 3-kinase (PI3-K) in the regulation of human sperm motility has been described. Therefore, the aim of this study was to investigate the role of PI3-K in boar sperm kinematics by using the specific PI3-K inhibitor, LY294002. Boar sperm was incubated up to 1 h in non-capacitating medium in the presence or absence of the cAMP analog, 8Br-cAMP or the PI3-K inhibitor, LY294002 or both. Boar sperm incubated in capacitating medium was treated in the presence or absence of LY294002. First, we have clearly identified that PI3-K is present in whole lysates of boar spermatozoa. Inhibition of PI3-K significantly increased boar sperm straight-line velocity, circular velocity and average velocity without an effect on the percentage of progressively motile spermatozoa in both media. Inhibition of PI3-K induced the same effects on boar sperm velocities as activation of the cAMP/protein kinase A (PKA) pathway and treatment with the PI3-K inhibitor, LY294002 had neither summatory nor synergic effects on boar sperm motion parameters when treated simultaneously with the cAMP analog 8Br-cAMP. Our data suggest that PI3-K plays a negative role, regulating boar sperm motion parameters through a possible inhibition of the cAMP/PKA activating pathway, and since some Computer Aided Sperm Analysis (CASA)-derived parameters have been related to field fertility our results point to the possibility of modulating sperm motile quality by modifying the PI3-K cellular pathway.

Boar sperm velocity and motility patterns under capacitating and non-capacitating incubation conditions

This study compares the velocity and motility of boar sperm under capacitating and non-capacitating incubation conditions. Aliquots of pooled, washed boar sperm were incubated in either Tyrode's complete medium (TCM; a capacitating medium), Ca2+-free TCM (TCM-Ca2+), or Ca2+ and NaHCO3-free TCM (Tyrode's basal medium [TBM]; a non-capacitating medium). Motility patterns were determined every hour over a 3h period of incubation at 38 degrees C. Capacitation status was assessed by the chlortetracycline assay after 1 and 3h of incubation. Experiments were repeated five times. Compared to the TBM control, a significant increase was seen in the percentage of capacitated sperm after 1h of incubation in TCM: the kinematics of these sperm cells were favorably modified. However, the motility patterns of sperm cells incubated in TCM and TCM-Ca2+ were very similar. Under capacitating conditions (TCM), the coefficients of linearity (LIN) and straightness (STR) significantly increased over time (LIN values were significantly different after 3h of incubation, while STR values were significantly different after only 2 h). Significant correlations were seen between LIN and the percentage of cells showing the B pattern (r = 0.334, P < 0.05) and the number of acrosome reacted spermatozoa (r = 0.301, P < 0.05). This suggests that capacitated boar spermatozoa may have a species-specific motility pattern.

Hepatocyte growth factor activates several transduction pathways in rat pancreatic acini

The receptor of hepatocyte growth factor (HGF), c-met induces different physiological responses in several cell types. Little is known about the role of HGF in exocrine pancreas. However, abnormal HGF signaling has been strongly implicated in pancreatic tumorigenesis and association of HGF with pancreatitis has been demonstrated. We have studied the presence of c-met and activation of their intracellular pathways associated in rat pancreatic acini in comparison with cholecystokinin (CCK) and epidermal growth factor (EGF). C-met expression in rat exocrine pancreas was identified by immunohistochemistry and immunoprecipitation followed by Western analysis. Tyrosine phosphorylation of c-met is strongly stimulated as well as kinase pathways leading to ERK1/2 cascade. HGF, but not CCK or EGF, selectively caused a consistent increase in the amount of p85 regulatory subunit of PI3-K present in anti-phosphotyrosine immunoprecipitates. Downstream of PI3-K, HGF increased Ser473 phosphorylation of Akt selectively, as CCK or EGF did not affect it. HGF selectively stimulated tyrosine phosphorylation of phosphatase PTP1D. HGF failed to promote the well-known CCK effects in pancreatic acini such as amylase secretion and intracellular calcium mobilization. Although HGF shares activation of ERK1/2 with CCK, we demonstrate that it promotes the selective activation of intracellular pathways not regulated by CCK or EGF. Our results suggest that HGF is an in vivo stimulus of pancreatic acini and provide novel insight into the transduction pathways and effects of c-met/HGF in normal pancreatic acinar cells.