Renin secretion by fetal lamb kidneys in vitro

Area of Science:

• Renal physiology
• Fetal development
• Endocrinology

Background:

• Renin is a key enzyme in the renin-angiotensin system, regulating blood pressure.
• Fetal kidney development and renin production are crucial for cardiovascular homeostasis.
• Understanding renin secretion mechanisms in fetal development is important for identifying potential issues.

Purpose of the Study:

• To investigate the renin content and secretion in ovine fetal kidneys at different gestational stages.
• To examine the effect of beta-adrenergic stimulation (isoproterenol) and cyclic AMP (dibutyryl cAMP) on renin secretion.
• To determine if developmental immaturity affects renin release mechanisms.

Main Methods:

• Renal cortical slices were obtained from immature (0.62-0.77 gestation) and mature (0.84-1.00 gestation) ovine fetuses.
• Renin content was measured in fresh tissue homogenates.
• Renin secretion was assessed by incubating slices in a medium with or without isoproterenol or dibutyryl cAMP.
• Renin levels were quantified using established biochemical assays.

Main Results:

• Immature fetal kidneys exhibited significantly lower renin content (24.3 ng/ml/h/mg) and basal renin secretion rates (1.4 ng ANG I/h/mg) compared to mature fetal kidneys (67.0 ng/ml/h/mg and 3.4 ng ANG I/h/mg, respectively).
• Renin content and basal secretion rates were strongly correlated in fetal kidneys.
• Isoproterenol and dibutyryl cAMP significantly increased renin secretion only in slices from mature fetuses, not immature ones.

Conclusions:

• There is a developmental increase in both renin content and basal secretion rate in ovine fetal kidneys.
• Immature ovine fetuses show a deficit in beta-adrenoceptor-mediated renin release, likely distal to cyclic AMP formation.
• This deficit in renin release mechanism may contribute to the lower renal renin content observed in immature fetuses.