Which of the following can inhibit the formation of myometrial gap junctions?

RRB Nsg. Superintendent - 29 April 2025 (Shift-3rd)

Obstetrics & Gynaecology

Easy

Appeared in: RRB Nsg. Superintendent - 29 April 2025 (Shift-3rd)

Explanation

Progesterone is the primary hormone responsible for maintaining uterine quiescence (relaxation) throughout most of pregnancy.
It actively suppresses the expression of genes for contraction-associated proteins (CAPs), including the protein Connexin-43.
Connexin-43 is the essential building block of myometrial gap junctions, which are channels that allow for coordinated electrical signaling and muscle contraction.
By inhibiting the formation of these gap junctions, progesterone prevents the myometrium from developing the synchronous contractions needed for labor.
This 'progesterone block' is crucial for carrying the pregnancy to term.

Option A: Prostaglandins are potent stimulators of uterine contractions and are involved in cervical ripening, initiating and promoting labor.
Option C: Estrogen has the opposite effect of progesterone. It promotes uterine contractility by increasing the number of gap junctions and oxytocin receptors as term approaches.
Option D: Oxytocin is a powerful hormone that directly stimulates uterine muscle contractions. Its action is dependent on the presence of gap junctions for coordinated activity, it does not inhibit their formation.

Visual 1: Diagram: A visual showing the hormonal balance during pregnancy versus labor. One side shows high progesterone inhibiting gap junctions and oxytocin receptors, labeled 'Uterine Quiescence'. The other side shows high estrogen promoting gap junctions and receptors, labeled 'Uterine Activation for Labor'.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Hormonal regulation of myometrial contractility and parturition as background academic context rather than a clinical decision trigger.
Understanding progesterone's role is critical for managing preterm labor risk. Synthetic progestins (e.g., 17-alpha-hydroxyprogesterone caproate) are sometimes administered to women at high risk for preterm birth to help maintain uterine quiescence.
Progesterone receptor antagonists, like mifepristone (RU-486), are used for medical termination of pregnancy because they block progesterone's effects, leading to cervical ripening and uterine contractions.
What if? If a patient is receiving a progesterone supplement to prevent preterm labor and starts experiencing regular contractions, it could indicate that the 'progesterone block' is failing and the body is beginning to transition towards labor, requiring immediate clinical assessment.

How to Approach the Question

First, identify the key concepts in the question: 'inhibit' (prevent or block) and 'myometrial gap junctions'.
Recall the function of myometrial gap junctions. They are protein channels that connect uterine muscle cells, allowing them to contract in a synchronized, coordinated way, which is essential for effective labor.
The question is asking which substance prevents the uterus from preparing for coordinated contractions.
Evaluate each option's primary role in pregnancy and labor.
Progesterone's main function is to maintain the pregnancy by keeping the uterus relaxed (quiescent).
Estrogen, prostaglandins, and oxytocin are all involved in stimulating or preparing the uterus for labor contractions.

Concept Tested & Keywords

Concept Tested: Hormonal regulation of myometrial contractility and parturition.
Stem keywords: inhibit, formation, myometrial gap junctions
Lead-in keywords: Which

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