Dominion Bankshares Corp., a Virginia bank holding company, and District of Columbia National Bank have reported record profits for 1976.

Not counting gains or losses from selling securities, Dominion earned $12.1 million $2.04 a share) in 1976 compared with $11.2 million ($1.88) the previous year. Counting securities transactions, the banking firm's profits were up 13.6 per cent to $2.09 a share from $1.84.

In the fourth quarter, Dominion operating profits rose 23 per cent to $3.2 million (54 cents) from $2.6 million (44 cents).

Chairman E. H. Ould attributed the gains to an improved interest margin (interest income less interest expenses). The Roanoke company's 12 banks operate 112 offices throughout the state.

D.C. National Bank reported a 31 per cent increase in earnings during 1976 to $436.455 ($2.18 a share) from $334,989 ($1.67) in 1975. Deposits rose to a record high $48.7 million compared with $46.2 million a year earlier.

Microdyne Corp., a Rockville producer of satellite television receivers, reported profits of $390,800 (34 cents a share) in the year ended Oct. 31, a gain of 48 per cent from $264,800 (23 cents) the previous year. Sales dipped to $4 million from $4.15 million. Microdyne said a Federal Communications Commission decision in December, permitting use of smaller earth terminals, is expected to result in sales increase.