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Pituitary-testicular axis in cardiomyopathic Syrian hamsters
A G Amador1, A Mayerhofer, A Bartke
1Department of Obstetrics and Gynecology, Southern Illinois University School of Medicine, Springfield 62794-9230.
Insights
Cardiomyopathic hamsters exhibit normal or enhanced testicular function despite pituitary deficiencies. Cellular calcium overload may stimulate Leydig cell gene transcription, including luteinizing hormone receptor (LHR) expression.
Area of Science:
- Endocrinology
- Cardiovascular Research
- Cellular Biology
Background:
- Cardiomyopathic hamsters possess a primary defect of intracellular calcium overload due to faulty voltage-sensitive calcium channels.
- Previous studies suggest potential endocrine dysregulation in these animals.
Purpose of the Study:
- To investigate testicular function and endocrine parameters in cardiomyopathic hamsters.
- To explore the impact of intracellular calcium overload on testicular function and hormone regulation.
Main Methods:
- Assessment of basal circulating hormone levels (gonadotropins, prolactin, thyroid hormones, progesterone, testosterone).
- Evaluation of luteinizing hormone receptor (LHR) autoregulation in response to human chorionic gonadotropin (hCG).
- Measurement of circulating testosterone levels following hCG administration.
Main Results:
- Lower basal levels of gonadotropin, prolactin, and triiodothyronine were observed in cardiomyopathic hamsters compared to controls.
- Thyroxine, progesterone, and testosterone levels did not differ significantly between groups.
- Luteinizing hormone receptor (LHR) autoregulation and testosterone response to hCG were enhanced in cardiomyopathic hamsters.
Conclusions:
- Cardiomyopathic hamsters demonstrate normal or more efficient testicular function despite impaired pituitary function.
- The cellular calcium overload in these hamsters may enhance Leydig cell gene transcription, particularly for LHR.
- This suggests a compensatory mechanism for testicular function in the face of cellular defects.
Abstract:
Testicular function and other endocrine parameters were studied in cardiomyopathic hamsters. In these animals, the major defect is an intracellular calcium overload, which is due to defective voltage-sensitive calcium channels. Basal circulating gonadotropin, prolactin, and triiodothyronine levels were lower in cardiomyopathic hamsters than in normal hamsters, but thyroxine, progesterone, and testosterone levels were not. In cardiomyopathic hamsters, the luteinizing hormone receptor (LHR) positive autoregulation by human chorionic gonadotropin (hCG) reached a maximum faster and at a lower dose than in normal hamsters. Similar results were observed for the response of circulating testosterone to hCG administration. The data indicate that, in spite of deficient pituitary function, cardiomyopathic hamsters have a normal or more efficient testicular function. This is probably the result of the cellular calcium overload, which would stimulate Leydig cell gene transcription, specifically that for LHR.