The corpus luteum is a transitory endocrine gland present in all vertebrate gravid females. Several authors have assigned a central role to the capacity to produce progesterone in egg retention during gestation and in the evolution of reptilian viviparity. However, its role in maintaining gestation in viviparous reptiles is currently under discussion. Here, we describe the effects of lutectomy on progesterone concentration and the maintenance of gestation in the temperate Mexican viviparous lizard Sceloporus grammicus
Materials and Methods: For this purpose, sixteen pregnant females were assigned to three different groups: lutectomy, sham lutectomy, or non-surgical treatment, the latter used as a control group. Blood samples were obtained before surgery, as well as 24 hours and 8 weeks after the procedure to determine the effects of lutectomy on the concentration of progesterone and the maintenance of gestation.
Results: We found a significant increase in the plasma concentration of progesterone 24 h after surgery (lutectomized and sham lutectomized lizards); however, these progesterone levels dropped significantly after 8 weeks. There were no significant changes in this regard in the control group at equivalent times when compared with the other groups. Normal parturition and no abortion events were observed in any of the study groups.
Conclusion: These observations indicate that the corpus luteum, although capable of progesterone production, is not necessary for the maintenance of gestation nor for parturition. Moreover, these results suggest the existence of a secondary source of progesterone capable of maintaining gestation.