Characterization of hormonal and molecular mechanisms modulating the hypothalamic-pituitary-ovarian function in bovine females

• Grant number: 24/22692-6
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• Start date: June 01, 2025
• End date: May 31, 2028
• Field of knowledge: Agronomical Sciences - Veterinary Medicine - Animal Reproduction
• Principal Investigator: Pietro Sampaio Baruselli
• Grantee: Lucas Oliveira e Silva
• Host Institution: Faculdade de Medicina Veterinária e Zootecnia (FMVZ). Universidade de São Paulo (USP). São Paulo , SP, Brazil

Abstract

The understanding of the physiological processes that regulate reproductive function in bovine females is essential for the development of biotechnologies aimed at optimizing reproductive and productive efficiency. The objective of this proposal is to characterize the hormonal and molecular mechanisms that modulate the hypothalamic-pituitary-ovarian (HPO) axis in bovine females. Therefore, in Study 1, two experiments will be conducted to evaluate the influence of progesterone (P4) on the steroidogenic capacity and metabolic profile of the dominant follicle, as well as the subsequent GnRH-induced LH surge in Bos indicus females. Pubertal Nelore heifers (n = 16) will be used in Latin square experimental designs (4 × 4; n = 16/treat). In Exp. 1, the heifers will be submitted to environments of low P4 (LP4), high P4 (HP4), decreasing P4 (DP4), and high P4 with hCG supplementation (HP4+hCG). In Exp. 2, the heifers will be submitted to environments of decreasing P4 in the presence (DP4+DF) or absence (DP4¿DF) of a dominant follicle, or high P4 in the presence (HP4+DF) or absence of a dominant follicle with estradiol (E2) supplementation (HP4+E2). Study 2 aims to characterize the molecular mechanisms underlying differences in HPO function among Bos taurus, Bos indicus, and crossbred heifers. Thus, pituitary tissue samples (previously collected) from Hereford (n = 6), Brahman (n = 8), and F1 Braford (n = 7) heifers will be submitted to laboratory analyses to determine the pituitary responsiveness to GnRH by assessing the expression of GnRH (GnRH-R) and E2 (ESR1) receptors, as well as the synthesis and storage capacity of LH, through the quantification of LH-¿ subunits. These studies will advance the scientific understanding of bovine reproduction to develop biotechnologies to enhance reproductive and productive efficiency. (AU)