Molecular mechanisms of labour

Question 1

Placental clock concept

Answer 1

Increased placenta CRH at term –> stim fetal pit to release ACTH –> increase fetal adrenal DHEA (oest precursor) secretion –> increase MGJ –> uterine contraction

Question 2

Flaw in PCC?

Answer 2

Anencephalic babies still deliver spont

Question 3

Message from baby?

Seen in mice

Answer 3

Fetal surfactant act amn macro which migrate to uterine wall and act inflam g.e. –> labour

Question 4

What happens during labour?

Answer 4

Cervix remodelled 
Pro-inflam needed 
Myocyte depol and increase IC ca
Increased MGJ
Change in myo responsiveness to prog

Question 5

Myometrial pro-quiescent mol

Answer 5

Prog, GaS, CRH, cAMP, PGE2, PKC, PKA, cGMP, NO

Question 6

Myometrial contractile-ass mol

Answer 6

Oest, CRH, Gaq, oxytocin, PGE2, PGF2a, Calcium, IP3

Question 7

3 stages of parturition

Answer 7

1. Cervical dilation
2. Fetal expulsion
3. Placental delivery

Question 8

What helps myometrial contractility?

Answer 8

Inflam
Differential g.e.
Elevated IC calcium (volt-gate calcium and IC stores from SR)

Question 9

Nifedipine

Answer 9

Ca channel blocker

Inhib prem myo contraction

Question 10

Oxytocin

Answer 10

Increase IC ca by releasing IC stores
Increase OTR on fundal myo
Released by cervical stim and myo stretch
Secreted from paravent nuc - postive FB

Question 11

OT and IC Ca

Answer 11

OTR activation –> IP3 act –> IP3R on SR –> Act Ca channels on SR –> IC Ca increase
PGF2a does same via FPR

Question 12

Atosiban

Answer 12

OTR antag, prevents premat contract via OTR

Question 13

Carboprost

Answer 13

Blocks PGF2a action

PPH

Question 14

Myometrial quiescence

Answer 14

Sig binds R in myo
Increase 2nd messenger mol 
Act enzymes that phos cell pt 
Dephos of myosin light-chain kinase 
Promoted by progesterone (stops MGJ, induces cAMP and impairs OT and PGF2a

Question 15

Antag of quies

Answer 15

1. oest - gap junc and OTR
2. CRH - general inflam
3. PGs
4. Calcium ions
5. Generalised inflam