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Photoperiodic Regulation of Compensatory Testicular Hypertrophy in Hamsters¹

Departments of Psychology³ Integrative Biology,⁴ University of California, Berkeley, California 94720 Department of Neurobiology and Physiology,⁵ Northwestern University, Evanston, Illinios 60208 Department of Population Medicine and Diagnostic Sciences,⁶ Cornell University, Ithaca, New York 14853

ABSTRACT

In mammals, removal of one testis results in compensatory testicular hypertrophy (CTH) of the remaining gonad. Although CTH is ubiquitous among juveniles of many species, laboratory rats, laboratory mice, and humans unilaterally castrated in adulthood fail to display CTH. We documented CTH in pre- and postpubertally hemi-castrated Syrian and Siberian hamsters and tested whether day length affects CTH in juvenile and adult Siberian hamsters. Robust CTH was evident in long-day hemi-castrates of both species and was preceded by increased serum FSH concentrations in juvenile Siberian hamsters. In sharp contrast, CTH was undetectable in short-day hemi-castrated Siberian hamsters for several months and only made its appearance with the development of neuroendocrine refractoriness to short day lengths; serum FSH concentrations of juveniles also did not increase above sham-castrate values until the onset of refractoriness. Long-day hemi-castrated Siberian hamsters with hypertrophied testes underwent complete gonadal regression after transfer to short days, albeit at a reduced rate for the first 3 weeks of treatment. Blood testosterone concentrations of adult hamsters did not differ between long-day hemicastrates and sham-castrates 9–12 weeks after surgery. We conclude that CTH is suppressed by short day lengths in Siberian hamsters at all ages and stages of reproductive development; in short day lengths, but not long day lengths, the remaining testis produces sufficient negative feedback inhibition to restrain FSH hypersecretion and prevent CTH.

compensatory testicular hypertrophy, follicle-stimulating hormone, inhibin, photoperiodism, reproductive axis, seasonal reproduction, testis, testosterone, unilateral castration

¹ Supported by Grant MH-61171 from the National Institute of Mental Health.

² Correspondence: Matthew J. Paul, Department of Neurology, University of Massachusetts Medical School, Worcester, MA 01655. FAX: 508 856 6778; matthew.paul{at}umassmed.edu

This article has been cited by other articles:

				M. J. Paul, J. Galang, W. J. Schwartz, and B. J. Prendergast Intermediate-duration day lengths unmask reproductive responses to nonphotic environmental cues Am J Physiol Regulatory Integrative Comp Physiol, May 1, 2009; 296(5): R1613 - R1619. [Abstract] [Full Text] [PDF]

				M. P. Butler, M. J. Paul, K. W. Turner, J. H. Park, J. R. Driscoll, L. J. Kriegsfeld, and I. Zucker Circadian Rhythms of Photorefractory Siberian Hamsters Remain Responsive to Melatonin J Biol Rhythms, April 1, 2008; 23(2): 160 - 169. [Abstract] [PDF]