Profits of American Security Corp., parent firm of American Security Bank in Washington, rose 15 percent in the second quarter of 1979.

Despite "uncertainties in the recent economic environment," ASC Chairman Carleton Stewart said yesterday, the banking firm's earnings growth continued on a consistent level as loan volume and deposits increased substantially.

In the April-June quarter, American Security earnings were $4.9 million ($1.35 a share) compared with $4.3 million ($1.17) a year earlier. Six-month profits rose 13 percent to $9.9 million ($2.70 a share) from $8.7 million ($2.39) in the first half of 1978.

Metropolitan Federal Savings and Loan Association, a Bethesda-based firm that is one of the largest thrift institutions in the Maryland suburbs, reported that higher interest costs cut down on earnings growth.

Profits for the second quarter were up just 1.7 percent to $551,539 ($1.23 a share) from $542,157 ($1.21) a year ago. Earnings for the first six months of 1979 were essentially unchanged from a year earlier at $1.09 million ($2.43 a share) in both periods.

Assets of Metropolitan rose 3 percent in the first six months to $252.6 million.

Directors approved a cash dividend of 12 1/2 cents a share, payable July 10 to owners of record June 30.