Messenger RNA content and complexity in normal and overloaded rat heart

Area of Science:

• Cardiovascular Biology
• Molecular Biology
• Gene Expression

Background:

• Cardiac overload, induced by abdominal aortic constriction in rats, leads to significant left ventricular hypertrophy (59% increase in weight).
• This condition precedes compensatory hypertrophy and involves dynamic changes in RNA metabolism.

Purpose of the Study:

• To investigate the changes in total RNA and poly(A)-containing messenger RNA concentrations and complexity during the development of cardiac overload.
• To analyze the frequency components of poly(A)-containing RNA in normal and overloaded hearts.

Main Methods:

• Rats underwent abdominal aortic constriction to induce cardiac overload.
• Quantification of total RNA and poly(A)-containing RNA concentrations at different time points (day 4, day 12).
• Hybridization of poly(A)-containing RNA to its cDNA copy, analyzed by Rot kinetics to determine sequence complexity and copy numbers.

Main Results:

• Total RNA and poly(A)-containing RNA concentrations increased significantly by day 4 post-constriction, peaking at 1.88 mg/g and 62 µg/g respectively, before returning to normal by day 12.
• Despite concentration changes, the total amount of both RNA types per ventricle remained elevated.
• Hybridization analysis revealed an increase in the number of RNA copies without altering the number of different gene sequences across frequency classes.

Conclusions:

• Cardiac overload stimulates an increase in poly(A)-containing RNA concentration, likely through enhanced transcription.
• The observed changes suggest a coordinated upregulation of gene expression, maintaining RNA complexity while increasing gene copy numbers.